Substitute 56 for A and 8 for b: $\displaystyle{56}=\frac{{1}}{{2}}\cdot{8}\cdot{h}\usepackage{cmbright}\Huge\$

Multiply both sides by 2: $\displaystyle{112}={8}\cdot{h}\usepackage{cmbright}\Huge\$

Divide both sides by 8: $\displaystyle{14}={h}\usepackage{cmbright}\Huge\$