well, we know that π is 180°, so then what is 3π/5?
[tex]\begin{array}{ccll} radians°rees\\ \cline{1-2} \pi &180\\ \frac{3\pi }{5}&x \end{array}\implies \cfrac{\pi }{~~ \frac{3\pi }{5}~~}~~ = ~~\cfrac{180}{x}\implies \cfrac{5\pi }{3\pi }=\cfrac{180}{x} \\\\\\ \cfrac{5}{3}=\cfrac{180}{x}\implies 5x=540\implies x=\cfrac{540}{5}\implies x=108[/tex]
