She should use 50% off.
964 divided by 1/2 = $482
964 - 400 = $564
Subtract x and mutiply v and add the answer
M= -8 - -5/ 3 - 15= -8+5/3-15= -3/-12 = 3/12 = 1/4
The slope is 1/4.
The slope formula is m=y2-y1/x2-x1. I plugged in -8=y2, -5=y1, 3=x2, and 15=x1. Then I solved it.
The missing side would be B = 15
