Tentukan: a. Nilai alfa, b. Besar sudut QOR, c. Besar sudut ROS

a. a + a + 20= 90
2a = 90-20
2a = 70
a = 35

b. QOR = TOU
TOU = a + 20
= 35 +20
= 55

c. ROS= (TOU + ROS) - 180
= (55 + 40) -180
= 95 - 180
= 85