R is the midpoint of line segment PT, and Q is the midpoint of the line segment PR. If S is a point between R and T such that the length of QS is 10 and the length of segment PS is 19, what is the length of segment ST?
P Q R S T
QS = 10
PS = 19
So
PS - QS = PQ
19 -10 = 9 = PQ
So QR = 9
PQ + QR = PR = 1/2 of PT
9 + 9 = 18 = PR = 1/2 of PT
So PT =36
PS - PR = RS
19 - 18 = 1 = RS
PQ + QR + RS + ST = PT
PS + ST = 36
19 + ST = 36
17 = ST
