Question

If in a triangle ABC, angle A+ angle B = 105° and angle B + angle C= 120°, then angle B is?

My attempt -

Angle A + Angle B = 105° ..... (1)

Angle B + Angle C = 120°
or Angle C = 120° – Angle B ........ (2)

Now, Angle A + Angle B + Angle C = 180° (Angle Sum property of a triangle)
or 105° + 120° - Angle B = 180° (Substituting values from (1) and (2))
or 225° - Angle B = 180°
or Angle B = 225° – 180° = 45°

I am doubtful of my solution. Can you please help me determine if I've solved it the correct way? I know it's a simple question, still silly doubts. Thanks!

Answer 1

Your method is correct and it is the correct answer
angle B is 45