Answer :
54 inches
Explanation
you can easily solve this by using a rule of three
let x represents the current heigth of the boy, then
if
[tex]45\text{ inches}\rightarrow100\text{ \%}[/tex]then
[tex]x\rightarrow120\text{ percent}[/tex]as the proportion is the same:
[tex]\begin{gathered} \frac{45}{100}=\frac{x}{120} \\ Multiply\text{ both sides by 120} \\ \frac{45}{100}\cdot120=\frac{x}{120}\cdot120 \\ 54=x \end{gathered}[/tex]so, the answer is 54 inches.
I hope this helps you