Tell someone to pick a positive integer, double it, add $9$, multiply by $5$ and then subtract the number that person started with. Tell that person to remove any nonzero digits in any order the person wishes. Then you tell the person the digit the person removed.
Explain how this is done.
So lets say the person pick $10$
doubling: $20$
add $9$: $29$
multiply by $5$: $145$
subtract beginning number: $135$
Lets say, the person removed $3$. So the person final answer would be $15$,
so how would i be able to tell the digits a person removed. the person could have removed $3$, $1$, $5$ as well.