In geometry, you can use the exterior angle of a triangle to find a missing interior angle. The following practice questions ask you to do just that, and then to apply some algebra, along with the properties of an exterior angle, to find a missing variable.

## Practice questions

Use the figure and the given information to answer the following questions.

In triangle

*WXY**,*In triangle

*WXY**,*Each angle is represented by the following:

Solve for the variable

*b.*

## Answers and explanations

70 degrees

The exterior angle of a triangle is equal to the sum of the two nonadjacent interior angles of the triangle, so set up an equation and solve for

*x:*Plug in the value for

*x*to find120 degrees

The exterior angle of a triangle is equal to the sum of the two nonadjacent interior angles of the triangle. Use this relationship to solve for

*a:*Plug in the value of

*a*to findThe angles of a triangle add up to 180 degrees. Therefore,