They values have a proportional relationship, as x increases by 4, y increases by five, giving a slope of 5/4. You can use the slope and a point given (I'll use (1,5)) in the equation y=mx+b to find the y-intercept, so solving for 5=5/4(1)+b you get 4.75 as your y-intercept. Simplified to slope intercept form y-5=5/4(x-1) is equal to our equation, so the answer is C.
