SOLUTION: Ana went shopping with X dollars and Y cents in her wallet. After spending half of her money on buying chocolate, she now has Y dollars and X cents. How much money did Ana spend on

There is no solution other than the silly solution that she 
had $0.00 to start with, the chocolate was free and she ended 
up with $0.00.

Here is why:

X dollars and Y cents  is 100X+Y cents.

Y dollars and X cents  is 100Y+X cents.

So half of 100X+Y equals 100Y+X

     (100X+Y) = 100Y+X

Multiply both sides by 2

      100X+Y = 200Y + 2X

         98X = 199Y

Divide by sides by 98Y

          = 

          = 

But that fraction won't reduce and can only equal to ,
where n is a positive integer. 

So the number of dollars must be 199n which is a 3 or more digit
number, which cannot be a number of cents, so there is no solution.

Edwin