Recall the definition of a parallelogram and its properties.
30
Practice makes perfect
Let's find the value of x.
Notice that the exterior angle measuring 45^(∘) and ∠ A are corresponding angles and therefore ∠ A = 45^(∘).
Since the given figure has two pairs of parallel sides, we can conclude that it is a parallelogram. Notice that ∠ A and ∠ B are consecutive. Theorem 6.4 says that the consecutive angles of a parallelogram are supplementary. Therefore, the measures of these angles add up to 180.
45+( 4x+15)=180
Let's solve the equation for x!
