We know that the triangle is made up of 180° To find "x" we need to know the two angles of the triangle. We also know that the supplementary angles are made of 180° In this case the supplementary angle would the angle were 100° and the missing value is. Since supplementary angles are made of 180° 180°-100° = 80° Now we know the two angles of the triangle. Since the triangle is made up of 180° 180° = x + 70° + 80° x + 150° = 180° x = 180° - 150° x = 30°
