In a ΔABC, ∠A + ∠B = 75° and ∠B + ∠C = 140°, then ∠B is:

Answer: Option B

∠A + ∠B = 75° . . . . . . (i)
∠B + ∠C = 140° . . . . . (ii)
(we know)
∠A + ∠B + ∠C = 180° . . . . . . (iii)
from equation (i) & (iii)
∠C = 105° . . . . . . . . . . . . . . . (iv)
from equation (ii) & (iv)
∠B = 35°