Question Number 12063 by tawa last updated on 10/Apr/17
Answered by b.e.h.i.8.3.4.1.7@gmail.com last updated on 11/Apr/17
$$\mathrm{100}+\mathrm{4}\left(\mathrm{180}−{a}\right)=\mathrm{360}\Rightarrow\mathrm{4}{a}=\mathrm{820}−\mathrm{360} \\ $$$$\mathrm{4}{a}=\mathrm{460}\Rightarrow{a}=\mathrm{115}\:\:\:\:.\blacksquare \\ $$