Which property of polynomial subtraction says that the difference of two polynomials is always a polynomial

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?

Af jewelry box is in the shape of a rectangular prism with an area of 528 cube inches. the length of the box is 12 inches and the height is 5 1/2 inches. what is the width of the jewelry box

Asporting good store is offering 30 percent off of the original price(x) of football cleats. the discount will be reduced by an another $7 before sales tax.