Hello, this is a typical word problem which requires you to use model drawing where student needs to understand that 5/7 of remaining money equates to 1/3 original. This is the key to the question.
The next step is to find the LCM of the denominators of 3 and 7 to be 21 and express the models in 21 units. After which student can work out the solution.
Do go through the thinking process with your kid to identify that as there are many problems related to this concept and solving method.
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