the present average age of a couple and their daughter is 35 years. Fifteen years from now, the age of the mother will be equal to the sum of present ages of the father and the daughter. Find the present age of mother?

A. 43 years
B. 40 years
C. 48 years
D. 45 years
E. None of these
Explanation:
(f + m + d)/3 = 35
=> f + m + d = 105 — (1)
m + 15 = f + d
Substituting f + d as m + 15 in (1), we get
2m + 15 = 105
2m = 90 => m = 45 years.