kerjakan no 20-22 dan pakai cara

20)
sudut BAC = 180°-120° = 60°
sudut ABC = 180°-125° = 55°
sudut ACB :
= 180°-(60°+55°)
= 180°-115°
=65° (A)

21)
A : B = 3 : 7
A : B = 3x : 7x
3x + 7x = 90
10x = 90
x = 90 : 10
x = 9
sudut A = 3x
= 3(9)
= 27°
sudut B = 7x
= 7(9)
= 63° (C)

22)
• a) = 3² + 4² < 8²
= 9 + 16 < 64 ( dapat )

• b) = 4² + 7² < 10²
= 16 + 49 <100 ( dapat )

• c) = 9² + 5² > 5²
= 81 + 25 > 25 ( tidak dapat )

• d) = 9² + 12² = 5²
= 81 + 144 = 225 (dapat)
jawabannya C