"This is much better."
Translation:Esto es mucho mejor.
Well, up to a point you may simply think that mucho mejor is an expression, what is called "locución adverbial" http://lema.rae.es/drae/srv/search?key=mejor, which is just fancy pants to name a bit of sentence that just works that way, though the words inside may work separately in other ways.
I'll just leave a couple of links and a bonus on mayor so you can do some reading http://lema.rae.es/drae/srv/search?id=96zEWGK0PDXX2z0jEyO4
Here's what confuses me about "mucho" vs. "mucho mas"... (forgive lack of accents or tildes in my Spanish in this forum)
I just missed a question about "He is tall, but his brother is much taller."
Correct answer: "El es alto, pero su hermano es mucho mas alto." (I missed the "mas" in that answer.)
Then, two questions later, I get this one ("This is much better"), and I put "Esto es mucho mas mejor," but I missed it because apparently using mas HERE is incorrect.
What is the difference between "better" and "taller"?
"mejor" is a comparative word that means better. We would normally use it to compare two things like "A is better than B".
On the other hand "alto" is not a comparative word. It is just a descriptive word that means tall. In order to make it comparative we just add the 'er' in English which produces the word "taller". However, in Spanish it seems we must add a separate word to create the comparative, i.e "muy alto".
consider the following:
tall = alto
taller = muy alto
much taller = mucho muy alto
better = mejor
much better = mucho mejor
This article recommends using the accents when referring to a known gendered noun (e.g. "ésta mesa"=this table) and using nonaccented neuter words when you're dealing with an unknown or nonspecific thing (e.g. "qué es esto"=what is this thing). http://spanish.about.com/od/pronouns/a/demonstrative_pronouns.htm However... the need for those accents actually seems to be debated. Duolingo doesn't seem to use the accents at all, and when I took Spanish in school I learned the words without accents. If anyone knows more, I'd love to hear their take.