Help please and explain?

F(x)=x/2-2 and g(x)=2x^2+x-3 find (f+g)(x)

John used linear combination to solve the system of equations shown. he did so by multiplying the first equation by -3 and the second equation by another number to eliminate the x-terms. what number did jonas multiply the second equation by? 4x-6y=23x+5y=11

Which equation results from adding the equations in this system? x+6y=9 and -x+2y=-15