The Total solution for NCERT class 6-12
∵ Sum of three angles of a triangle = 180°∴ (x –40)° + (x – 20)° + (x-10)0 = 180°
⇒ x –40° + x – 20° + x – 10° = 180°
⇒ x +x+ x – 70° = 180°
⇒ x = 180° + 70° = 250°
⇒ x= = 100°
∴ x =100°