Find two numbers if their ratio is 9:11 and their and their difference is 6

What is the measure of ac? 5 units 13 units 26 units 39 units

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?

Math it's appreciated. (picture provided)