(-2r/3s/5):5

careful about multip-layered fractions like

5/6/7
Does it mean (5/6)/7 or does it mean 5/(6/7), they are not the same

following the standard rule re division and multiplication as "left to right" in the order they occur, your
(-2r/3s/5) would be (-2r/3)(s/5) = -2rs/15
then:
(-2r/3s/5):5
= -2rs/15 : 5
= -2rs : 75