3x² + 5x - 7 how do i answer this question.

Combine like terms
8x^2-7
Then I think this works.

You need to know what X is equivalent to. in this EXAMPLE I will use 2

3(2 squared) + 5(2) - 7

3(4) + 10-7

12 + 10 - 7

22 - 7 = 14

the answer is 14  IF X EQUALS 2

X might not equal two in your case