SAT math question?

a ( a + b + 2) + b (a + b + 2) + 2 (a + b + 2)

a² + ab + 2a + b² + ab + 2b + 2a + 2b + 4

a² + b² + 2ab + 4a + 4b + 4

((a+b) + 2)^2 = (a+b)^2 + 2*(a+b)*2 + 2^2 =
(a^2 + 2ab + b^2) + (4a+4b) + 4

The parentheses in the last line above are not needed.

Note: I am using the formula (A+B)^2 = A^2 + 2AB + B^2
with A=(a+b) and B=2.

You didn't say what we are supposed to do?

If you are supposed to expand that expression out fully, just multiply the terms. I'd do it by distributing:
a(a + b + 2) + b(a + b + 2) + 2(a + b + 2)
a² + ab + 2a + ab + b² + 2b + 2a + 2b + 4

Then combine like terms:
a² + (ab + ab) + (2a + 2a) + b² + (2b + 2b) + 4
= a² + 2ab + 4a + 4b + b² + 4

But perhaps there is something else you are supposed to do?

Rule
(x+y)^2 = x^2+2xy+y^2