The same number of each type of notes were used (18 pieces)

So, the difference between the number of $10 and $2 notes is unchanged.

Ratio of $10 to $2 now
= 3 : 1

Difference = 3 units - 1 unit = 2 units

Ratio of $10 to $2 to difference now
= 3 : 1 : 2



At first,

Ratio of $10 to $2
= 5 : 2

Difference = 5 units - 2 unit = 3 units

Ratio of $10 to $2 to difference at first
= 5 : 2 : 3

We have to change the ratio to make the units for the difference equal.

We have :

5 : 2 : 3 for at first.
3 : 1 : 2 for now


The smallest common multiple of 3 and 2 is 6.


So,

At first
5 : 2 : 3 → multiply by 2 → 10 : 4 : 6

Now
3 : 1 : 2 → multiply by 3 → 9 : 3 : 6



Number of units of $10 or number of units of $2 used

= 10 units - 9 units = 1 unit

(Or 4 units - 3 units = 1 unit)


1 unit = 18 notes

So there were 10 units of $10 notes and 4 units of $2 notes at first.


Value of the $10 notes

= $10 × 10 units × 18 notes per unit

= $1800


Value of the $2 notes

= $2 × 4 units × 18 notes per unit

= $144



Amount of money Xiaoli had at first

= $1800 + $144
= $1944