F(X) = -20x^2 + 14x + 12
G(X) = 5x - 6
F(g(X)) = F(5x - 6) = -20(5x - 6)^2 + 14(5x - 6) + 12.
-20(5x-6)(5x-6) + 70x - 84) + 12
-20(25x^2 - 60x + 36) + 70x - 84 + 12
- 500x^2 + 1200x - 720 + 70x - 84 + 12
-500x^2 + 1270x - 720 - 72
-500x^2 + 1270x - 792.
The domain, I believe is all real numbers. As the graph eventually touches all values of X.