Kx+ 6y = 12; 0.75x + 1.25y = d solve for k and d

This is so hard and it’s for a test

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?

Rose bought a new hat when she was on vacation. the following formula describes the percent sales tax rose paid b=t-c/c