The translation 'have you had to buy this' does not seem correct. 'You had to buy this?' Or 'did you have to buy this?' Seem more appropriate
You cannot abbreviate you had to you'd. You'd is an abbreviation of you would.
If we accept "Have you had to buy it" (and we always put such 'full' answers into Incubator, no abbreviations), the algorithm automatically accepts "you'd", unfortunately. Nothing we can do about it.
On the previous page in red, where it says my answer is incorrect, it says the correct translation is "We'd to buy it". I agree with "Did you have to buy it?" as it says above, but as a native speaker I've never heard We'd to buy it!
That's a Duolingo-wide bug caused by the fact that the algorithm doesn't understand context.
OK, so if you write "We had done it", you can abbreviate it to "We'd done it", right? So the algorithm automatically accepts "We'd done it" even if this abbreviated form wasn't explicitly put among the accepted answers.
So here, the accepted answer is "We had to buy it"... and the algorithm not only accepts "We'd to buy it", but may even suggest it :/ And all this is because it doesn't understand that this is not a situation in which "we had" may be abbreviated.
I hope they will finally fix this...