Exercise 22 Page 58

Two angles are supplementary if the sum of their measures is 180^(∘). With this in mind, we can create an equation to demonstrate this relationship. m∠ 3 + m∠ 4= 180^(∘) We can find m∠ 4 by substituting the given value, m∠3=56^(∘), into the equation.

m∠ 3 + m∠ 4= 180^(∘)

Substitute

m∠ 3= 56^(∘)

56^(∘) + m∠ 4= 180^(∘)

SubEqn

LHS-56^(∘)=RHS-56^(∘)

m∠ 4= 124^(∘)

The measure of ∠ 4 is 124^(∘).