If angle QR is 180° and arc QR is 10z, set them equal to find the value of z
180 = 10z; divide both sides by 10
18 = z
Then use this value in 6z to find the arc SPT
6(18) = SPT
108 = SPT
Since this is a central angle, the arc length and angle measurement are the same. Therefore angle SPT = 108°
(Also, hey XD)