Tolong dijawab ya no 20, 21, 22 pakai cara nya ya, terimakasih

20. sudut aoc + sdt cob = 90°
3x - 15 + 2x + 5 = 90
5x - 10 = 90
5x = 100
x = 20 °
sdt boc = 2x + 5
= 2×20 + 5
= 40 + 5
= 45°(c)

21. L adb = a×t÷2 = 9×8÷2 = 36 cm^2
L ade = 9×12÷2 = 54 cm^2
L adc = 9×2÷2 = 9 cm
L yang diarsir = Ladb + Lade - 2Ladc
= 36 + 54 - 2×9
= 90 - 18
= 72 cm^2 (c)

22 tinggi dinding^2 = 5^2 - 3^2
= 25 - 9
= 16
tinggi dinding =
[tex] \sqrt{16} [/tex]
= 4 cm
kemiringan tangga terhadap dinding = 4/3 (d)


kemiringan = gradien = y/x