Introduction to Geometry: Rays and Angles

think icon Think & Click: Angle Bisectors

Now, you try. Complete the Think & Click activity by looking at the problem below, thinking about it, and then clicking on the question to reveal the solution.

MC is the bisector of AMB. Using the information given below, find x.
angle A M B with angle bisector M C, making two angles with measures x plus 20 and 3 x minus 40
 

Since MC is the bisector of AMB, then the measure of angle A M C equals the measure of angle B M C. Replacing the measures in this equation, we obtain

x + 20 = 3x - 40
Add 40 to each side, and simplify.
x + 20 + 40 = 3x - 40 + 40
x + 60 = 3x
Subtract x from each side, and simplify.
x + 60 - x = 3x - x
60 = 2x

x = 30

View this tutorial on angle addition: