7a+[4a-6b-(8a+2b)]
ok so you would get this
7a+[4a-6b-8a-2b]<--- distribute the negative
therefore
7a-4a-8b
3a-8b<---solution
ok so you would get this
7a+[4a-6b-8a-2b]<--- distribute the negative
therefore
7a-4a-8b
3a-8b<---solution