Question

The age of a father is 4 years more than three times of his son’s age. Three years ago, father age was five times of him son’s age. Find the present age of each of them

Answer 1

Suppose that $x$ is the age of the father and $y$ is the age of the son. Then we have the following system of equations:

$\left\{\begin{matrix} x=3y+4 \\ (x-3)=5(y-3) \end{matrix}\right.$

We substitute expression for $x$ from the first equation into the second and receive:

$3y+1=5y-15$.

It implies that $y=8$ . Using the first equation of the system we get $x=28$ .

Answer: x=28, y=8.