You don't "lenite the adjective to transform it into a predicate".
Attributive adjectives agree with their nouns in case, number and gender. Predicative adjectives are not modified.
A nominative singular masculine attributive adjective is not modified, and is otherwise indistinguishable from the equivalent predicative adjective, though usually context is more than sufficient to avoid any ambiguity, but go deacair is unambiguously predicative.
Why would this be the case, though? I also answered "I make the question difficult". Is it because in one sentence (I make the question difficult) something is being done to the object ("question"), and in the other sentence (I do the difficult question), "difficult" is describing the object that the subject is acting on? Is this what causes the lenition?
Apologies, I'm just trying to understand this.
You're on the right track with
"in the other sentence (I do the difficult question), "difficult" is describing the object that the subject is acting on?"
In English, you have two types of adjectives. Attributive adjectives go immediately before the noun they modify, while predicative adjectives go in the predicate. In most sentences, the predicate is simply everything from the verb to the end of the sentence.
For example, in "the difficult question" difficult is an attributive adjective, while in I make the question difficult, the same word is a predicative adjective.
In Irish, the distinction is not marked by placement of the word deacair, but rather by whether or not the word is lenited: attributive adjectives that modify female nouns in the nominative and accusative cases are lenited, while predicative adjectives are not lenited (as far as I understand).
Sorry for the long post.
Does that mean that in the (nominative) case of masculine nouns, there is no way to visually distinguish between attributive and predicative adjectives, because neither form would be lenited? And that you would need to rely on context to know which one is being meant?
First example that comes to mind: Déanaim an bia deacair. Can this mean both "I make the food difficult." (=I write a tricky recipe) and "I make the difficult food." (=I struggle with cooking it myself)?
Yes, you've pretty much got it. The difference is between attributive and predicative adjectives. In "In make the difficult question," "difficult" is attributive and modifies "question." The adjective is closely linked to the noun it describes and in Irish, if that noun is feminine, it causes lenition if the adjective can be lenited. If the adjective is predicative - it is linked to the noun by "to be" or another verb, the connection between the noun and the adjective is broken and the adjective is not lenited.
I make the good question (attributive) - Deanaim an chest mhaith I make the question good (predicative) - Deanaim an cheist maith
When you are taking a written test or exam, you "do" the questions on the exam - "There were 15 questions, but I only had time to do 12 of them" - "Did you do the question on Othello?" "I did all the geometry questions as quickly as possible, so that I'd have more time to do the algebra questions". Déan is used in the same way in Irish. That usage doesn't apply when someone asks you a question (in English or in Irish).
You can use the verb fiafraigh or you can use ceist a chur to ask or put/pose a question.
Examples from the NEID entry for "ask".
"she asked him if he saw anything" - chuir sí ceist air an bhfaca sé rud ar bith,d'fhiafraigh sí de an bhfaca sé aon rud
"he asked the time" - d'fhiafraigh sé cén t-am é, chuir sé ceist cén t-am é
"that's what we're asking ourselves now" - sin an cheist atáimid a chur orainn féin anois, sin an rud atáimid a fhiafraí dínn féin anois
I notice that the new speaker is saying Deinim which is what was said in my area when we were growing up. Déanaim is the caighdeán oifigiúil version.
Couldn't this also be "loosely" translated as "I do the hard question"?
Yes, it should be accepted. Ó Dónaill gives both "hard" and "difficult" for deacair. The word for hard in the sense of "hard as iron" is crua.
But it's precisely because "hard" has these different meanings in English that it is helpful to learn that deacair is "difficult" (which is one of the things that we use "hard" for in English) and crua means "not soft" (which is one of the things that we use "hard" for in English) and dian means "intense" or "severe" (which is one of the things that we use "hard" for in English), etc. If you start off learning that deacair means "hard", you can get into trouble when you need one of the other meanings of "hard".
dhea at the beginning of a word is sounded as if the 'dh' were a 'y'. mar dhea is a common phrase in Irish where it occurs.
If you see a 'h' following a consonant then you know that consonant has been lenited.
My question is why was the "d" and the "y" both pronounced in this case?
They weren't. The speaker makes a 'y' sound. I am not a linguist so I am not familiar with the notation you used but I do know how Irish is pronounced. I grew up in an area where Irish words were used daily in English conversation. My grandfather was more fluent in Irish than he was in English.