Answer
$C \approx36.2^\circ$, one triangle.
$A\approx 43.8^\circ$
$a \approx3.51$
Work Step by Step
1. Use the Law of Sines, we have $\frac{3}{sinC}=\frac{5}{sin100^\circ}=\frac{a}{sinA}$
2. $C=sin^{-1}(\frac{3sin100^\circ}{5})\approx36.2^\circ$ only one triangle.
3. Find the third angle $A\approx180-100-36.2=43.8^\circ$
4. $a=\frac{5sin43.8^\circ}{sin100^\circ}\approx3.51$
