Answer
See below.
Work Step by Step
$B=180-A-C=180-43-83=54^\circ$.
Using the law of sines, $\frac{a}{\sin43^\circ}=\frac{12}{\sin54^\circ}\\a=\frac{12\sin43^\circ}{\sin54^\circ}\approx10.12$
$\frac{c}{\sin83^\circ}=\frac{12}{\sin54^\circ}\\c=\frac{12\sin83^\circ}{\sin54^\circ}\approx14.72$
