Answer: A
Explanation:
Since we know that T is the midpoint of SU, we know that it bisects SU. Now, we know that it cuts SU in half. With that, we know that ST and TU are equal.
3x=2x+20 [subtract both sides by 2x]
x=20
Now that we know x, we can plug them in to solve for each segment.
ST
3x [plug in x=20]
3(20) [multiply]
60
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TU
2x+20 [plug in x=20]
2(20)+20 [multiply]
40+20 [add]
60
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SU
60+60=120
We know that SU is ST and TU combines, therefore, we add the values of ST and TU.