Question

a+b+c=100
a+b=80
b+c=70

Answer 1

c=100-(a+b)
c=100-80
c=20

a=100-(b+c)
a=100-70
a=30

b=70-c
b=70-20
b=50

Answer 2

Daca a+b+c=100 si a+b=80 => c=100-80=20
B+c= 70 => b=70-20=50
A+b=80=> a=80-50=30