Question

if qrs/r=s and q=0 what must be true?

Answer 1

Then r=0 and s=0

Answer 2

Although s = 0, r can be any number. The r's will cancel each other out, leaving you with qs = s. If q = 0, anything times q = 0. If the s on the right = 0, so must the s on the left.

e.g., (0 * 9 * 0)/9 = 0