(-2x^2 + x + 31) + (3x^2 + 7x -8) = ax^2+bx+c
Simplify the left side of the equation:
-2x^2 + 3x^2 + x + 7x + 31 -8 = x^2+8x+23
Now you'll see that 'a' will have to be 1 (since the coefficient for x^2 is 1)
'b' = 8 (coefficient for x)
'c' = 23 (the constant in the equation)
Add them up!
1+8+23= 32
Hope this helps!
