https://hoc24.vn/hoi-dap/question/250597.html
A = 9999931999 - 5555571997
9999931999 = ....31999
....31999 = (.... 34)499 x ....33
....31999 = ...1499 x ....7
...1499 = ....1
....31999 = ....1 x 7 = ...7
5555571997 = ....71997
....71997 = (.... 74)499 x ....7
....71997 = ....1499 x ....7
....1499 = ....1
....71997 = ....1 x ....7
....71997 = ....7
A = 9999931999 - 5555571997
A = ....7 - ...7
A = ....0
....0 ⋮ 5
Vậy A ⋮ 5