Dacă a+b+c=198 b-c=123 afla 2a+b+3c

a+b+c=198
b-c=123...=> b=c+123
2a+b+3c=?
a+c+123+c=198
a+2c+123=198
a+2c=198-123
a+2c=75
a+b+c+a+2c=198+75
2a+b+3c=273