Which fraction is equivalent to 4 over negative 15

What are the measures of ∠a, ∠b, ∠c and ∠d? explain how to find each of the angles. measure need asap

How is working backward similar to solving an equation?

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?