This looks like an assignment to me.
Your best interest is to try to solve the problem yourself. Give it your best shot.
If you get struck, post your solution and we can point out what the problem is.
Good luck! :)
Okay, I won't let you go "empty handed".
Here are some pointers:
- You can do the programming part. If you've never done any C++, check out some tutorial. E.g.: https://www.w3schools.com/cpp/
- The maths part is a bit tricky. Mostly, because the problem description is not really specific: "prints the smallest number if one digit is removed". What does this mean?
Let's assume you have a number 321. What is "the smallest number if one digit is removed"? Is it [32]1? Is it 3[21]? Or [31] by removing 2 from the middle? Or can it be [12] by removing 3 and reordering the digits?
Anyway, you need to first find out what you need to do. Then you can think about how the maths work. Then write the code for it.