In △ABC, m∠B - 120°. Ratio between m∠A and m∠C is 5 : 7, then m∠A is _____?

35°

15°

25°

None of these

Given Data:

m∠B = 120°

Ratio of m∠A : m∠C = 5 : 7

Step-by-Step Solution:

Triangle Angle Sum Property:

m∠A + m∠B + m∠C = 180°

m∠A + 120° + m∠C = 180°

m∠A + m∠C = 60°

Solving Using Ratio:

Let m∠A = 5x and m∠C = 7x

5x + 7x = 60

12x = 60

x = 5

Finding m∠A:

m∠A = 5 × 5 = 25°