Question

The lesser to two numbers is $31$ less than three times the greater. If the numbers differ by $7$, what is the lesser number?

Answer 1

Let the lesser number be $a$ and the higher number be $b$
We have $b-a=7$ and $a=3b-31$
By substituting value of $b$ from equation (1) in equation $2$, we get

$a=3(7+a)-31$
$\Rightarrow a=21+3a-31$

$\Rightarrow a=5$