Answer:
Let X be other interior opposite angle of a △XYZ.
Let Y be the third angle.
Exterior angle is equal to sum of interior opposite angles.
120
o
=30
o
+∠X
⇒∠X=90
o
Now, Sum of interior angles of a triangle is 180
o
⇒90
o
+30
o
+∠Y=180
o
⇒∠Y=180
o
−120
o
=60
o
Step-by-step explanation:
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