a-b=862
a:b=5 r 6...=> a=5b+6
5b+6-b=862
4b+6=862
4b=862-6
4b=856
b=856:4
b=214
a=214*5+6
a=1070+6
a=1076
1076-214=862
1076:214=5 r 6
a:b=3 r 3...=> a=3b+3
c:b=2 r 7...=> c=2b+7
a-c=738
3b+3-2b+7=738
b-4=738
b=738+4
b=742
a=742*3+3
a=2226+3
a=2229
c=742*2+7
c=1484+7
c=1491
2229:742=3 r 3
1491:742=2 r 7
2229-1491=738
