1. Given (12+3)x, we can sum the numbers in the parenthesis to get 15x
2. Given 12x+3x, we can factor x to get (12+3)x and get the same as 1.
3. Given (12+3x)x, we have to distribute the x and we have 
4. This expression is already simplified.
We have -4(x - 6) + 3(a - 7) = -4x + 24 + 3a - 21 = -4a + 3a + 3
so the answer is B
ok done. Thank to me :>
The ratio to this problem is 750:216
Answer: you would use the last option