Answer:
a=3 i think, sorry if i'm wrong
Explanation:
4x-2(x+a)=8 ~parenthesis first.
4*7-14-2a=8 ~4 times 7= 28 and just bring down the rest.
28-14-2a=8 ~ add 14 to negative 14 and 8, the positive and negative 14 would cancel out each other.
28-2a=22 ~ subtract 28 from both positive 28 and 22.
-2a=-6 ~ divide by 2 on both sides.
a=3 ~ The reason why it is 3 is because negative 2 times positive 3 equals negative 6.