Asurvey of 392 children given at a local elementary school showed that 175 like chocolate ice cream, 125 like pistachio ice cream, and 142 do not like chocolate or pistachio ice cream. how many children like at least one kind of ice cream mentioned in the survey?

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.