Isabel joins a service to download movies. she pays $2 per movie, but she gets the first 5 movies for free. how many movies, m, can she download for $50? three of these equations give the correct value of m. which equation does not?

To find the equation, identify the slope and the y-intercept.

The slope is the coefficient to the variable. When you see the word 'per', you know that 2 is the slope, as she is paying 2 dollars per movie. This, in mathematical terms, is represented as 2x. 

The y-intercept is the amount she starts off with. She gets 5 for free, so the y-intercept is +5. 

The equation is 

To solve for c = 50, plug 50 in and subtract 5 from both sides:



m = 22.5

21/2 or 5/2