Slope of AB=(2-3)/(1+1)=-1/2; AC=(-1-3)/(-3+1)=-4/-2=2; BC=(-1-2)/(-3-1)=-3/-4=3/4.
The product of two sides that are perpendicular is -1. Slopes of AB and AC are perpendicular so angle A is a right angle. ABC is a right-angled triangle.
I could be wrong but this is what I think.
D=RT
D=39 (3)
D=117
Infinity, because there is no set amount of years the price can rise. The price and keep rising as long as he rents, and it's stated that he will not ever buy a house
Calculators op. 585/18=32.5
C and D apply to your expression.