One sample of n= 10 scores has a mean of 8 and a second sample of n= 5 scores has a mean of 2. If the two samples are combined, what is the mean for the combined sample?

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?