First we can pass the information we have to inches so:
[tex]10ft\cdot\frac{12}{1}=120\text{inc}[/tex]So the sum of heigths is 124 inches, so we can write a equation for each condition so:
[tex]\begin{gathered} A+B=124 \\ A-B=10 \end{gathered}[/tex]Where A is the height of the big brother and B is the height of the small brother so we can solve bout equation for A so:
[tex]\begin{gathered} 1\to A=124-B \\ 2\to A=10+B \end{gathered}[/tex]Now we can made the equation equal so:
[tex]\begin{gathered} 10+B=124-B \\ 2B=124-10 \\ B=\frac{114}{2} \\ B=57 \end{gathered}[/tex]So the small brother is 57 inches
