Answer and Step-by-step explanation:
1.
I see the Vertical Angles Theorem being used with the angle of 19 and angle y.
Vertical Angles Theorem states that angles that are vertical to each other are congruent to each other.
I see the Complementary Angles Theorem being used with the angle y and angle z.
Complementary Angles Theorem states that angles that are next to each other and are split by a line of a right angle will add up to 90 degrees.
2.
y = 19
y + z = 90
Substitute 19 for y.
19 + z = 90
Subtract 19 from both sides of the equation.
z = 71
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