tolong nomor 11dan 12 dan rumusnya

11)3a+20+2a=180
5a+20=180
5a=160
a=160/5
a=32
Jadi besa
12. 5x+3x+12=180
8x+12=180
8x=168
x=21°
Sudut pelurus = =3(21)+12=75°

11. (3a+20) + 2a = 180°
 = 3a + 2a =180 - 20
 = 5a = 160
 a = 160/5
 a = 32
ABD = (3×32+20)
ABD = 116°
12. 5x + (3x+12) = 180°
 = 5x + 3x = 180 - 12
 = 8x = 168
 x = 168/8
 x = 21
SQR = (3×21+12)
SQR = 75°