The answer is 100(X + 48)/(X + 48 + Y), where X and Y are given by:

(X - 70)/Y = 3/4 .... (1)

X/(Y - 112) = 8/7 .... (2)

Part of your job is to figure out what X and Y represent and where these two equations have come from. The other part is to solve equations (1) and (2) for X and Y.