Download Write and solve an algebraic equation to find the missing angles.

7.G.5
Use facts about supplementary, complementary, vertical, and adjacent angles in a multi-step problem to
write and solve simple equations for an unknown angle in a figure.
Supplementary angles: Two angles are supplementary if the sum of their degree measures is 180.
Find the missing angles. Use an algebraic equation.
Complementary angles: Two angles are complementary if the sum of their degree measures is 90.
Find the missing angles. Use an algebraic equation.
PRACTICE: Write and solve an algebraic equation to find the missing angles.
1.
2.
3. Find the complement of each angle.
Angle
4. Find the supplement of each angle.
Angle
Complement
85°
87°
13°
130°
x°
y°
(2x + 40)°
(3x + 5)°
Supplement
5. Find the measure of the third angle of each triangle in which the measures of the two angles of the
triangle are given.
Angle 1
Angle 2
Angle 3
16°
42°
90°
30°
x°
y°
x°
(x + 20)°
6. One of the congruent angles of an isosceles triangle measures 37°. Find the measures of the other
angles. Draw and label a picture to model the problem. Write and solve an equation to find the missing
angle.
7. An angle measures 38° less than its complement. Find the measures of the two angles. Draw and label a
picture to model the problem. Write and solve an equation to find the missing angle.
8. One angle of a triangle measures 10°more than the second. The measure of the third angle is twice the
sum of the first two angles. Find the measure of each angle. Draw and label a picture to model the
problem. Write and solve an equation to find the missing angle.
9. Find the measure of angle that is 10° more than its complement. Draw and label a picture to model the
problem. Write and solve an equation to find the missing angle.
10. Find the measure of an angle that is 30° less than its supplement. Draw and label a picture to model
the problem. Write and solve an equation to find the missing angle.