Johathan purchases 10 traveler's checks in denominations of $20, $50, and $100, totaling $370.He has twice as many $20 checks as $50 checks. How many of each denomination of traveler's checks does he have?

Lin 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= 3/12= 0.25 step 2 y= 0.25x where did joylin make her first error?