tentukan panjang PS...cm

Diketahui:
QS = 3 cm
ST = 8 cm
OR= 12 cm

Ditanya:
PS?

Penyelesaian:
PS/PQ = TS/QR
PS/(PS+QS) = TS/QR
PS/(PS+3) = 8/12
12xPS = 8x(PS+3)
12PS = 8PS +24
12PS-8PS = 24
4PS = 24
PS = 24/4
PS =6 cm