Question

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?

Answer 1

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
`c = 2m+5.`

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


`45 = 2m`

m = 22.5