Use the expression $\frac{5}{9}(F - 32)$ to evaluate some Celsius temperatures. You may use degC for $^{\circ}\mathrm{C}\text{.}$

1. If a temperature is $50{^\circ}\mathrm{F}$ what is that temperature measured in Celsius?
2. If a temperature is $-20{^\circ}\mathrm{F}$ what is that temperature measured in Celsius?