Question

Finding Missing Angle Measures
Find m∠DBC.

Line B D intersects line A C at point B. Angle A B D is (2 x) degrees and angle D B C is (x + 90) degrees.

What is the m∠DBC?

mAngleDBC =
°

Answer 1

Lines BD and AC form a linear pair at B, so the two given angles sum to 180°:
2x + (x + 90) = 180
3x + 90 = 180
3x = 90
x = 30

m∠DBC = x + 90 = 30 + 90 = 120°

Answer: 120°