The information gives you two equations:

$\displaystyle{B}+{R}={40}\usepackage{cmbright}\Huge\$ and $\displaystyle{B}-{R}={14}\usepackage{cmbright}\Huge\$

Add the equations: $\displaystyle{2}{B}={54}\usepackage{cmbright}\Huge\$ , so $\displaystyle{B}={27}\usepackage{cmbright}\Huge\$

Substitute 27 for B in the first equation: $\displaystyle{27}+{R}={40}\usepackage{cmbright}\Huge\$ , so $\displaystyle{R}={13}\usepackage{cmbright}\Huge\$