Question

$A$ is $20$ years older than $B$. $5$ years ago, $A$ was $3$ time as old as $B$. Find their present age.

Answer 1

Lets $A^{\prime }s$ present age be $x$ years
And $B^{\prime }s$ present age be $y$ years
According to the question
$x=y+20$
$x-y=\mathrm{20.....}\left(1\right)$
Five years ago,
$x-5=3(y-5)$
$x-3y=-10.....\left(2\right)$
Subtracting $\left(1\right)$ from $\left(2\right)$,
$x-3y=-10.....\left(2\right)$
$x-y=20......\left(1\right)$
$-+-$
______________
$-2y=-30$
$y=15$
From $\left(1\right)$
$x=15+20$
$x=35$
Thus, present ages of $A$ and $B$ are $35$ years and $15$ years.