Answer
$B\approx36.2^\circ$
$C\approx63.8^\circ$
$c\approx4.55$
Work Step by Step
1. Use the Law of Sines $\frac{5}{sin80^\circ}=\frac{3}{sinB}=\frac{c}{sinC}$
2. Thus $B=sin^{-1}(\frac{3sin80^\circ}{5})\approx36.2^\circ$
3. Find the third angle $C\approx180-80-36.2=63.8^\circ$
4. $c=\frac{5sin63.8^\circ}{sin80^\circ}\approx4.55$
