Use this rule: \(a \times \frac{b}{c}=\frac{ab}{c}\).
\[\tan{60}=\frac{DG}{20+X}\]
Multiply both sides by \(20+X\).
\[\tan{60}(20+X)=DG\]
Divide both sides by \(G\).
\[\frac{\tan{60}(20+X)}{G}=D\]
Switch sides.
\[D=\frac{\tan{60}(20+X)}{G}\]
D=(tan(60)*(20+X))/G
