Let us consider 3 cases
Case1
5 comes at hundreds place
So now we have 9(0,1,2,3,4,6,7,8,9)options to fill the tens place and 9 places to fill ones place
So 1×9×9=81 ways
Case2
5 comes at tens place
Now hundreds place can be filled with 8 options (1,2,3,4,6,7,8,9 not zero as then it will become a 2 digit number) and 9 ways to fill ones place
So 8×1×9=72
Case 3
5 comes at ones place
So again 8 ways to fill hundreds place and 9 ways to fill tens place
8×9×1=72
So total ways =81+72+72= 225 ways
Hope it helps
