5 years ago the average age of a family which includes father, mother and a son was 35 years. 3 years ago the average age of father and mother was 46 years. What is the present age (in years) of the son?

Let age of father, mother and son respectively be $$f,m,s$$ years

Average age of father, mother and son 5 years ago = 35 years

=> Sum of present ages of father, mother and son = $$(35+5)\times3$$

=> $$f+m+s=120$$ ------------(i)

Similarly, sum of present ages of father and mother = $$(46+3)\times2$$

=> $$f+m=98$$ ---------(ii)

Subtracting equation (ii) from (i), we get :

=> $$s=120-98=22$$ years

=> Ans - (D)