Exercise 3 Page 304

Notice that ∠ 4 and ∠ 5 form a linear pair.

The Supplement Theorem tells us that they are supplementary angles, and we get the following relation. m∠ 4+m∠ 5 = 180 Now, let's substitute m∠ 4= 2x and m∠ 5= x+9 into this equation and solve for x.

Finally, we find the measures of ∠ 4 and ∠ 5 by substituting x= 57 into their expressions. lll m∠ 4=2x & ⇒ & m∠ 4=2( 57) & & =114 m∠ 5=x+9 & ⇒ & m∠ 5= 57+9 & & =66