Jackson owes his sister Monica $15. Monica has a $10 in her pocket. Explain the meaning of zero in this situation.

The only zero I see here is in the 10$.

Here, it's a place holder, to show the real value of 1: if there was no "0", you would say that she has only 1 in her pocket.

but by filling the one's place with a digit, we "move" the 1 to the ten's place: which means that she will have 1 time 10, so 10 dollars (ten)