It takes 45 seconds. the easiest way to do these is to use a graphic calculator and replace the variables with x and y, for example, this equation would become -5x^2+30x, and if you don't have access to a graphing calculator, you can always use desmos online.
You didn’t show a picture of the graph, although the equation would be y=-1/2x+2
so every two x spaces forward you should go down one y space and the y should start at 2 when x = 0
First the original price is reduced by 15%
assume the original price is x
100%-15%=85%..u r left with 85% of the price
thus,85/100 multiply x
the reduced price is reduced again by 5%
so,95/100 ×(85/100 x)=$315.32
find x
323/400 x =$315.32
×=$390.49