Question

johnny's age is three times Alex's age. The sum of their ages is 72. What is Alex's age?

Answer 1

Assume that Alex's age is x

Since Johnny's age is three times Alex's age, so Johnny's age is 3 x

Since the sum of their ages is 72, add their ages and equate the sum by 72

$x\text{+3x = 72}$$4x=72$

Divide both sides by 4 to find x

$\begin{gathered} \frac{4x}{x}=\frac{72}{4} \\ x=18 \end{gathered}$

So Alex's age is 18 years