Exercise 56 Page 637

We are given that in △ ABC, ∠ B is a right angle and ∠ A is 20^(∘) greater than ∠ C. If we call the measure of ∠ C x, then the measure of ∠ A is ( x+ 20). Let's recall that the sum of the angle measures in a triangle is always 180^(∘). m∠ A+m∠ B+m∠ C=180^(∘) ( x+ 20)+90+ x=180 Next, we will solve the above equation for x.

(x+20)+90+x=180

▼

Solve for x

RemovePar

Remove parentheses

x+20+90+x=180

AddTerms

Add terms

2x+110=180

SubEqn

LHS-110=RHS-110

2x=70

DivEqn

.LHS /2.=.RHS /2.

x=35

The value of x is 35. Therefore, the measure of ∠ C is 35^(∘). This corresponds with answer B.