tolong dijawab,caranya juga ditulis

130 = 2x + 40
130 - 40 = 2x
90 = 2x
x = 45

40 = y + 10
40 - 10 = y
30 = y
y = 30

3z + 20 = 80
3z = 80 - 20
3z = 60
z = 20

x+y-z = 45 + 30 - 20 = 55 derajat