Question -
Answer -
In a ∆ABC ,
∠A = x°, ∠B = 3x° and ∠C = 7°
But ∠A + ∠B + ∠C = 180° (Sum of angles of a triangle)
=> x + 3x + y = 180
=>4x + y = 180 ………(i)
and 3y – 5x = 30 ….(ii)
from (i) y = 180 – 4x
Substituting the value of y in (ii)
3 (180 – 4x) – 5x = 30
540 – 12x – 5x = 30
=> -17x = -540 + 30 = -510
=> 17x = 510
=> x = 30
y = 180 – 4x = 180 – 4 x 30 = 180 – 120 = 60
∠A = x = 30°
∠B = 3x = 3 x 30° = 90°
∠C = y = 60°
∠B of ∆ABC = 90°
∆ABC is a right angled triangle.