b + 200 = 400 – 100
b = – 100 + 400 – 200
b = 100
c – 40 = 100 – 80
c = – 80 + 100 + 40
c = 60
75 + a = 800 – 700
a = – 700 + 800 – 75
a = 25
b + 200 = 400 – 100
b = – 100 + 400 – 200
b = 100
c – 40 = 100 – 80
c = – 80 + 100 + 40
c = 60
75 + a = 800 – 700
a = – 700 + 800 – 75
a = 25