I don’t know the answer

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.

i'm not really sure how to answer that

step-by-step explanation:

the answer is a. 72. but i cant answer with less than 20 characters so here's some random text talking about it.