m∠A=(2x-30)°
m∠B=(x+20)°
m∠C=(x-10)°
Sum of angles of triangle is 180°
So, m∠A+m∠B+m∠C=180°
So, (2x-30)°+(x+20)°+(x-10)°=180°
4x°-40°+20°=180°
4x°-20°=180°
Adding 20° on both sides
So, 4x°-20°+20°=180°+20°
4x°+0°=200°
4x°=200°
To find the value of x,
So, x=200/4
x=50
So, m∠A=(2*50-30)°=100°-30°=70°
m∠B=(x+20)°=50°+20°=70°
m∠C=(x-10)°=50°-10°=40°
Answer:Option C
