Angles ABM and CBM adjacent BS- bisector of angle ABM. Find the CBS angle if the MBS angle is 30 degrees.

By condition, the angles ABM and CBM are adjacent, that is, their sum is 180 degrees.

BS is the bisector of the angle ABM. The obtained angles CBS and MBS are also adjacent, since the BS side is their common side, and the other two sides CB and MB are a continuation of each other (based on the adjacency of the ABM and CBM angles).

Thus, the sum of the adjacent angles CBS and MBS is:

CBS + MBS = 180,

and taking into account the fact that the MBS angle is equal to 30 degrees,

you can calculate the degree measure of the CBS angle:

CBS = 180 – MBS = 180 – 30 – 150 degrees