in the triangle on the right side,
90° + (3x+12)° + (4x+8)° = 180° [we used 4x+8 in this triangle, cus vertically opposite angles are equal]
90 + 7x + 20 = 180
110 + 7x = 180
7x = 180 - 110
7x = 70
x = 70/7
x = 10°
hope it helps...!!!
