Rate of change y=-4.5+15 x y 1.5 5 2.5 10 3.5 15 4.5 20 5.5 25

You could increase your chances of getting the help you need and want if you'd please be sure to include the instructions for each problem.

y = -4.5 + 15 would be a linear function whose rate of change (slope) is -4.5 if you had included the "x" after -4.5:     y = -4.5x + 15.  Compare this to 
                                                             y = mx    + b

Seems as tho' you have shared five possible "solutions."  None of them would satisfy    y = -4.5x + 15.  

I'd suggest you go back to the original problem and ensure that you've copied it down here exactly as it was presented there.

He will need 2,898 pieces of paper