Let me try to help you
This question deals with the concept we call constant difference. Constant difference happens when usually 2 parties (or more) give away or receive the same quantity of items or objects. Constant difference also happens in age, where the age difference remains the same between 2 (or more) parties.
This question is dealing with constant difference, as we can see that both of them have spent the same amount of money buying the same item. Hence the difference in amount of money they have before and after will be the same.
Do note that they had a difference of $70 – $42 = $28 at first. They will still have a difference of $28 in the end.
Their ratio at the end is 5 : 1. This means that the difference of 4 units would represent the difference in money that they have, which is $28.
Since 4 units represents $28, 1 unit would represent $7.
Ivan had 1 unit of money left in the end, that would also mean he has $7 left.
Hope this helps!
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