tentukan x, y, z, t ,,

(y+30)+(2x+60) = 180
y + 2x + 90 = 180
y + 2x = 90
       y = 90 - 2x
(y + 30) + t + y = 180
2y + 30 + t = 180
2(90-2x) +30 + t = 180
180-4x + 30 +t = 180
-4x +30+ t = 0
-4x + t =  -30
4x - t = 30
       t = 4x - 30

begitu juga
t + z = 180
4x-30 + z = 180
4x+z = 180+30
4x+ z = 210
      z = 210 - 4x