CPhill helped me before. I need you to go on please. I can't figure it out.

OK..... f(3) means we put 3 into the function and evaluate this....so we have

2(3)^2 - 4(3) + 9  = 2*9 - 12 + 9  =  18 -12 + 9 = 15

And 2f(3) means we multiply this result by 2....so 2*15 = 30

And f(-3) means to do a likewise thing...so we have

2(-3)^2 - 4(-3) + 9 = 18 + 12 + 9 =   30 + 9 = 39

And 3f(-3) means to multiply this result by 3 = 39*3 = 117

So   2f(3) + 3f(-3)  =  30 + 117  =   147