On the left, first distribute the 8 to both terms to get 8*3a + 8*6 which =
24a+48.
Now you distribute on the right side to get 9*2a - 4*9 which = 18a - 36.
Now you set them both equal to get 24a+48 = 18a - 36
Get your a-terms together by subtracting 18a from both sides to get 6a+48=-36
Then subtract 48 from both sides and get 6a=-84. Divide by 6 and get
a = -14