if two digit positive integers have their tens digits exchanged, the difference between the resulting pair of integers differs of the difference between the original pair of numbers by4, what's the greatest possible difference between the original pair of integers?
answers:76;80;82;90;94.
答案给出的感觉是逐个试出来的。。。这个有没有更系统一点的办法来算啊。
谢谢大家!