The country recreation department cleared a 3/4 mile long walking trail in washington park. if the trail will be marked every 1/12 mile with a small sign, how many signs are needed?

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.

2 is the final ! : )

b. 153 students do not participate in sports and seventy-five 12th graders were surveyed