Answer
See below.
Work Step by Step
$A=180-60-73=47^\circ$.
Using the law of sines, $\frac{a}{\sin47^\circ}=\frac{20}{\sin60^\circ}\\a=\frac{20\sin47^\circ}{\sin60^\circ}\approx16.89$
$\frac{c}{\sin73^\circ}=\frac{20}{\sin60^\circ}\\c=\frac{20\sin73^\circ}{\sin60^\circ}\approx22.08$
