A number N has three digits when expressed in base 7. When N is expressed in base 9 the digits are reversed. Then the middle digit is
https://web2.0calc.com/questions/find-a-base-7-three-digit-number-which-has-its-digits-reversed-when-expressed-in-base-9-you-do-not-need-to-indicate-the-base-with-a-subscr
Wish I found this link before spending 30 min on this....