Multiply both sides by 3: $\displaystyle{3}\cdot{V}={3}\cdot\frac{{1}}{{3}}{B}{h}\usepackage{cmbright}\Huge\$

Simplify: $\displaystyle{3}{V}={B}{h}\usepackage{cmbright}\Huge\$

Divide both sides by h : $\displaystyle\frac{{{3}{V}}}{{h}}=\frac{{{B}{h}}}{{h}}\usepackage{cmbright}\Huge\$

Simplify: $\displaystyle\frac{{{3}{V}}}{{h}}={B}\usepackage{cmbright}\Huge\$