posted by Vince .
Mary's age is 2/3 that of peter's. Two years ago Mary's age was 1/2 of what Peter's age will be in 5 year's time. How old is peter now?
Let P=peter's age, and
Two years ago, Mary's age was M-2, and it was what Peter's age will be in 5 years time (P+5)/2
M-2 = (P+5)/2
Substitute M from (1)
(2/3)P-2 = (P+5)/2
Solve for P to get P=27, and M=18