......Repede............

a+b=1246
a-b=1234 a= 1234+b
1234+b+b=1246
1234+2b=1246
2b=1246-1234
2b=12
b=12:2
b=6
a+6=1246
a=1246-6
a=1240
proba: 1
240+6=1246
1240-6=1234