Betty has a cow . the cow produces 5 liters of milk each day . if his diet improved , the cow will produce 200% more milk . how much milk will he produce in a day , if that were to happen ? this is not a proportion problem.

check the picture below.

well, the angle at the vertex d is clearly not a right-angle, let's check for the one at the vertex f which does look like,   however if it's indeed, that means ef is perpendicular to df, in which case their slopes will be negative reciprocal of each other.

so the negative reciprocal of the slope of ef is 1, however the slope of df is not 1, is 1/2, so nope, they're not perpendicular lines.