How can i show her numbers are related to each other

You can show the relation of both number by simply identifying th place value of each digits.
For example, the number is 555.55
=> First 5 in the left has a hundreds value, followed by tens and ones.
=> then the number next to decimal point has a value of tenths and the next is hundredths.

Now, how the find the relationship of the given number
=> Each number has 10 times difference with each other.
=> 0.05 x 10 = 0.5
=> 0.5 x 10 = 5
=> 5 x 10 = 50
=> 50 x 10 = 500
=> 555.55

If jon had $4.00 then takes away $2.25, then he should have $1.75 left. $4.00 - $2.25 = $1.75 hope this ; )