Both form straight angles, which are 180 degrees.
x+4y+x+y=180
2x+5y=180
4x+y=180
Solve the second equation for y and substitute the variable.
y= -4x+180
2x+5(-4x+180)=180
2x-20x+900=180
-18x= -720
x=40
Plug the x value in
4(40)+y= 180
160+y=180
y=20
Final answer: x=40, y=20
