Answer:
ST = 16
Step-by-step explanation:
We'll assume STU is a straight line:
S<---x+8--------->T<-----8------->U
<---------------3x------------->
ST + TU = SU
(x+8) + 8 = 3x
x + 16 = 3x
2x = 16
x = 8
S<---8+8--------->T<-----8------->U
<---------------3*8------------->
ST = 16
