Let n be the number then 5n-68=n, so subtract n from each side: 4n-68=0. Now add 68 to each side: 4n=68.
Divide through by 4: n=17. So the number is 17.
To check, multiply 17 by 5=85. 68 less than this is 85-68=17, which is the number. So the solution is correct.