5. Find mTOS in the figure below.

Applying the definition of a linear pair, m∠TOS = 52°
Recall:
Linear pair are two angles on a straight line whose sum equals 180°.
Given:
m∠TOU + m∠TOS = 180° (linear pair)
128° + m∠TOS = 180°
m∠TOS = 180° - 128°
m∠TOS = 52°
Thus, applying the definition of linear pair, m∠TOS = 52°
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