Question

a+b+c=90
a+2b+c=120
2a+b+c=110
a,b,c =?

Answer 1

a+b+c=90 -> a = 90-b-c

a+2b+c=120

2a+b+c=110

90-b-c+2b+c=120

2*(90-b-c)+b+c=110

b = 120-90

180-b-c=110

b=30

180-30-c=110

150-110 = c

40 = c

a = 90-40-30

a = 20