Question

P(x) = 3x2 - 7x + 11, find P(9).

Answer 1

You need to substitute 9 with every x value in the equation. 
So, 3(9)^2-7(9)+11
p(x)= 191

Answer 2

$P(9) = 3\cdot9^2-7\cdot 9 +11 = 3\cdot 81 - 63 +11 = 243-63 + 11 =\\=180+11=191$