Answer:
Answer: B. 54 deg
Explanation:
The sum of the measures of the angles of a triangle is 180 degrees. The triangle shown has one angle measuring 72 degrees. The other two angles have unknown measures, but they both measure y. Since the same variable y is used for both of the unknown angles, that means the two measures are equal.
We use the fact above about the sum of the measures to set up an equation.
y + y + 72 = 180
Add like terms.
2y + 72 = 180
Subtract 72 from both sides.
2y = 108
Divide both sides by 2.
y = 54
Answer: B. 54 deg
Check: 54 + 54 + 72 = 180, showing that 54 is correct.