Răspuns :
a-b=47
a:b=3 r 7
a=3b+7
3b+7-b=47
2b+7=47
2b=47-7
2b=40
b=40:2
b=20
a-20=47
a=47+20
a=67
a:b=3 r 7
a=3b+7
3b+7-b=47
2b+7=47
2b=47-7
2b=40
b=40:2
b=20
a-20=47
a=47+20
a=67
a-b=47
a:b=3 rest 7 => a=3b+7
3b-7-b=47
2b-7=47
2b=47-7
2b=40
b=40:2
b=20 => a=3*b+7=3*20+7=60+7=67
verificare:67-20=47
a:b=3 rest 7 => a=3b+7
3b-7-b=47
2b-7=47
2b=47-7
2b=40
b=40:2
b=20 => a=3*b+7=3*20+7=60+7=67
verificare:67-20=47