# A man who is 42yrs old has a son of 12yrs old in how many years will the father be twice as old as his son?

Sep 10, 2015

Let's set the required number of years to $x$

#### Explanation:

After $x$ years the father will be $x + 42$ years old
The son will then be $x + 12$ years old

We can now set up the equation:
$x + 42 = 2 \cdot \left(x + 12\right) \to$
$x + 42 = 2 x + 24 \to$
Now subtract $x$ from both sides, and then subtract $24$
$42 = x + 24 \to 18 = x \to x = 18$ years