what number must you subtract from -13 to get a difference of 0? so i know the answer to this part; its -13 but i dont know how i got that answer like i dont know how to explain it please help :sob:

Dexter read 11 science fiction books and 5 history books. lena read 9 science fiction books and 4 history books. compare the students’ ratios of science fiction books to history books. 1. determine the ratios’ form:    science fiction books to history books 2. write the ratios as fractions:    dexter: 115; lena: 94 3. rewrite with a common denominator. 4. compare. 5. answer the question. determine which shows the correct comparison of the ratios for this problem.

Acar started driving from city a to city b, distance between which is 620 miles, at a rate of 60 mph. two hours later a truck left city b and started moving towards city a at a rate of 40 mph. how many hours after the truck's departure will the two meet?

Joey is asked to name a quadrilateral that is also a rhombus and has 2 pairs of parallel sides.should be his answer