Explain to me how you got the anwser

The difference of 2 numbers is 21 and the quotient of the equation is 4 then what are the two numbers?

Isuck at math ; ^; m a student solved this problem and said the answer is 3 feet. chase had a roll of ribbon that contained 7 7/8  feet of ribbon. he cut off one piece that was 3 5/8  feet long and another piece that was 1 1/4  feet from the roll. how much ribbon was left on the roll? is the student's answer reasonable? yes, the answer is reasonable. no, the answer is not reasonable. it should be about 2 feet. no, the answer is not reasonable. it should be about 13 feet. no, the answer is not reasonable. it should be about 4 feet.

Anna is constructing a line segment that is congruent to another segment ab. for the construction, which tool should be used to mesure segment ab