The average age of husband, wife and child 7 years ago was 42 years and that of wife and child 9 years ago was 36 years. The presentage of the husband is:

Let the present age of husband = $$x$$

the present age of wife =$$y$$

 and the present age of child = $$z$$

then according to question, $$\dfrac{(x-7)+(y-7)+(z-7)}{3} = 42 $$ 

$$\Rightarrow x+y+z = 126 + 21$$

$$\Rightarrow x +y +z = 147 $$           ......... equestion (1)

again according to question $$\dfrac { (y-9) + (z-9)} {2} = 36 $$  

$$\Rightarrow y +z -18 = 72 $$

$$\Rightarrow y +z = 90  $$         ........... equestion (2)

so  equestion (2) subtract from equestion (1)

then $$x +y + z - y -z = 147 - 90 $$ 

$$\Rightarrow x = 57 $$ 

then the present age of husband = 57 Ans