y = 4x+5 is in the form y = mx+b which is slope intercept form. Anything in y = mx+b form is linear. It graphs out a straight line.
Contrast this with y = x^2 which is nonlinear because it graphs a curve that isnt a straight line. All quadratics like this graph out a parabola which resembles a bowl shaped curve.
The correct answer is 66.
The equation is 12.5n where n stands for any hour that Phil is riding his bike. I'm using the nth term here though.
