You can do addition and substraction operations with polynomials similarly as with simple real numbers.
First of all you have to open brackets and then you can add numbers (-7-4=-11). Then the result is following:
The percentage of buttons that are large is 75%.
A^2 + 3b + c - 2d
(3)^2 + 3(8) + (2) - 2(5)
9 + 24 + 2 - 10 = 25