besar sudut ABC adalah a.34° b.8° c.78° d.84° jawab no 12 tolong...

12) 180° = 39° + 3x + 4x - 6
180° = 7x - 33
180 - 33 = 7x
147 = 7x
x = 21

Besar sudut B = 4x21 - 6 > 84 - 6 = 78° (C)

13) 180° = 2x + 4x
180° = 6x
x = 30

Sudut QOR = 2 x 30 = 60°

Bab Garis dan Sudut
Matematika SMP kelas VII


3x + 39 + (4x-6) = 180
7x + 35 = 180
7x = 147
x = 21.

Nilai = 4x - 6
= 4(21) - 6
= 84 - 6
= 78 derajat (C)