Four expressions are shown below:
a. 4(8x + 2)
b. 4(7x +3 )
c. 32x + 8
d. 28x +12 which two expressions are equivalent to 4(7x + 2+ x)?

We'll just have to compare each expression to see if they manipulate into the provided equation.

a) 4(8x+2) compared to 4(7x + 2 + x)

In 4(7x + 2 + x) we can add the x values to create this equation. (7x + x = 8x). This is a correct answer.

b) There's no way we can manipulate 2 + x to become 3 (without solving for x of course). This is not equivalent. 

c)32x + 8 compared to 4(7x + 2 + x)
4*7x is 28x, so that doesn't work. But remember in a) we could add 7x+x = 8x. So 4*8x = 32x, then 4*2 = 8. So this one is also equivalent.

We don't need to check D, since we have our two valid options (as directed by the question.)

Maybe the answer is 20mm. all i really did was just multiply, which is obvious.