Answer:
pr = 4.
Explanation:
If pq=7 and qr=28 then what is pr?
qr / pq = r/p = 28/7 = 4.
prq^2 = 7 * 28 = 196
196 = 2 * 2 * 7 * 7
q^2 is a perfect square so looks like it could be 49 then pr would be 4.
Since r/p = 4 then r = 4 and p = 1 would suit the equalities.
Checking with the given information: pq = 1 *7 = 7 and qr = 7*4 = 28 so we have the right answer.