McGraw Hill Integrated II, 2012
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McGraw Hill Integrated II, 2012 View details
3. Tests for Parallelograms
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Exercise 18 Page 500

Recall the Parallelogram Opposite Angles Theorem says that if a quadrilateral is a parallelogram, then its opposite sides are congruent.

x=2
y=29

Practice makes perfect

Let's find the value of each variable one at a time.

Value of y

Notice that the angles that measure 106 and 3y+19 are opposite angles. Recall the Parallelogram Opposite Angles Theorem says that if a quadrilateral is a parallelogram, then its opposite angles are congruent. Therefore, for the figure to be a parallelogram, the measures of these angles must be equal. 106=3y+19 Let's solve the above equation.
106=3y+19
87=3y
29=y
y=29

Value of x

Notice that the sides with lengths x+11 and 2x+9 are opposite sides in our quadrilateral. Recall the Parallelogram Opposite Sides Theorem says that if a quadrilateral is a parallelogram, then its opposite sides are congruent. Therefore, the lengths of the opposite sides must be equal. x+11=2x+9 Let's solve the equation.
x+11=2x+9
11=x+9
2=x
x=2