lihat gambar nomor 16 dan 17

16) 40 + 5x + 3x = 180 ===> 8x = 140 ===> x = 17,5

maka Sudut ABD ===> 40 + 5x = 40 + (5 x 17,5) = 127,5 ... ( C )

17) 5x + 21 + 2x - 2 = 180 ===> 7x + 19 = 180 ===> x = 23

maka Sudut BCD = 2x - 2 ===> (2 x 23) - 2 = 44 ... ( B )

No 16 :
40° + 5x + 3x = 180°
40° + 8x = 180°
8x = 180°-40°
8x = 140°
x = 140°/8
x = 17,5

<ABD = 40° + 5x
<ABD = 40° + 5(17,5)
<ABD = 40° + 87,5
<ABD = 127,5° (C)


No 17 :
2x-2 + 5x+21 = 180°
2x+5x-2+21 = 180°
7x+19 = 180°
7x = 180-19
7x = 161
x = 161/7
x = 23

<BCD = 2X-2
<BCD = 2(23)-2
<BCD = 46-2
<BCD = 44° (B)