Joylin is writing an equation to model the proportional relationship between y, the total cost in dollars of downloading videos from a website, and x, the number of videos downloaded. She knows that the total cost to download 3 videos was $12. Her work to find the equation is shown below. Joylin’s Work

Step 1
k = StartFraction 3 over 12 EndFraction = 0.25
Step 2
y = 0.25 x

Where did Joylin make her first error?

Step-by-step explanation:

Jocelyn was attempting to find out how much she will be charged per download. She has the fraction upside down. To find the amount of money per download, the fraction should be $12/3downloads to get $4/1download. That is the slope of the equation, the rate of change or, for us, the fact that your cost will go up $4 for every single video you download. The equation would then be

y = 4x

The way she has it, we are paying only a quarter for a download. If that be the case, for 3 downloads we would only be paying .75, but it says we pay $12, so we know something is wrong right there.