Solve with substitution 3x + y =19 -6x - 5 = y​

If f(x)=-x^2+6x-1 and g(x)=3x^2-4x-1,find(f+g)(x)

Ineed me i stuck and i don’t want to get it wrong

Isabel graphed the following system of equations. 2x – y = 6 y = -3x + 4 she came up with the solution (2,-2). what were the 3 steps she did to get that solution? (make sure they are in the correct order)