Anyone know the answer to this simple little equation? it's giving me a bit of a tough time.. 3x^2 (4x-7)

I'm so close to finishing all these.

Combine like terms to make a simpler expression 3z+z

In order for the function to be linear, what must m be and why? m = 22 because the rate of change is 1. m = 20 because the rate of change is 3. m = 22 because the rate of change is -1. m = 20 because the rate of change is -3.