How do you get the answer for this equation a+2b+(14a-5b)-[6a+6b-(a+4)]

first, it's not an equation. Sure clue: no = sign!

However, if you just want to simplify,

a+2b+(14a-5b)-[6a+6b-(a+4)]
a+2b+14a-5b-[6a+6b-a-4]
a+2b+14a-5b-6a-6b+a+4
10a-9b+4