In this case, we can wee that
[tex]5a+4a=\text{ 180}[/tex]
hence,
[tex]\begin{gathered} 9a=180 \\ a=\frac{180}{9} \\ a=20 \end{gathered}[/tex]
On the other hand, we can also see that
[tex]x+4a=180[/tex]
since a=20, then
[tex]\begin{gathered} x+4(20)=180 \\ x+80=180 \\ x=180-80 \\ x=100 \end{gathered}[/tex]
