Prove that the set of points A(3,3),B(1,-2),C(-5,-2) and D(-3,3) be the vertices of parallelogram

Daniel bought a computer game for $25 and later sold it to thomas for a 40% profit. how much did daniel sell the computer game for?

Suppose that one doll house uses the 1 inch scale, meaning that 1 inch on the doll house corresponds to 1/2 foot for life-sized objects. if the doll house is 108 inches wide, what is the width of the full-sized house that it's modeled after? in inches and feet.

X+ y = 5 ; x - y =3 solve using linear combination