12a
Since the question is 3(2a), then just write it out. 3(2a) is 2a+2a+2a or 6a.
10
2a x 3 = 24= 6a = 24(divide both sides by 6)a = 4
I guess you mean: 2a^2+6a Well in this case you take 2a out of the bracket and then you're left with a+3 inside. 2a(a+3a)
6a squared-8ab+2a factor completely and check mentally