The total inner angle for a triangle is 180°.
So to find x,
40° + 2x + 2x + 20 = 180°
2x + 2x = 180° - 40° - 20
4x = 120°
x = 120° ÷ 4
x = 30°
∆CAB = 2x
= 2 (30)
= 60°
∆ACB = 2x + 20
= 2(30) + 20
= 60° + 20
= 80°
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