Exercise 7 Page 599

According to the Triangle Sum Theorem, the sum of the measures of the interior angles of a triangle is 180^(∘). From the previous exercises, we know that two of the angles in △ XYZ are 33^(∘) and 124^(∘). Using the theorem, we can write the following equation. 33^(∘)+124^(∘)+m∠ Z=180^(∘)Let's solve this equation.

33^(∘)+124^(∘)+m∠ Z=180^(∘)

AddTerms

Add terms

157^(∘)+m∠ Z=180^(∘)

SubEqn

LHS-157^(∘)=RHS-157^(∘)

m∠ Z=23^(∘)

Now we can copy and complete the statement: m∠ Z = 23^(∘).