1)
[tex]\it if\ u=the\ interior\ angle \Rightarrow 180^o-u = the\ exterior\ angle \\ \\ u=\dfrac{(10-2)\cdot180^o}{10}=8\cdot18^o=144^o\\ \\ \\ 180^o-144^o=36^o\ (the\ size\ of\ each\ exterior\ angle)[/tex]
2)
[tex]\it \dfrac{(n-2)\cdot 180^o}{n}=120^o \Rightarrow \dfrac{n-2}{n}=\dfrac{\ 120^{(30}}{180} \Rightarrow \dfrac{n-2}{n}=\dfrac{4}{6} \Rightarrow n=6\ sides[/tex]
