tolong jawab no. 15,16 pakar cara . . . . untuku nomor 16 besar

15.
7x + 40 = 180
7x = 180 - 40
7x = 140
x = 140/7
x = 20

2y + 80 + 40 = 180
2y = 180 - 80 - 40
2y = 60
y = 60/2
y = 30

2y + 40 + 4z = 180
2(30) + 40 + 4z = 180
60 + 40 + 4z = 180
4z = 180 - 60 - 40
4z = 80
z = 80/4
z = 20

x + y + z = 20 + 30 + 20
= 70, jawabannya D

16.
3x + 4x + 5 = 180
3x + 4x = 180 - 5
7x = 175
x = 175/7
x = 25
jadi jawabannya A