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Amy and Brian go to shop to buy a bag. However, Amy is 200 short, and Brian is 2400 short.
Even if they combine their money, they still can't afford the bag. How many pesos does the bag cost?
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It is a classic entertainment problem, but in your post it is posed INCORRECTLY.
With this condition the problem HAS NO a unique solution.
Some vitally important part is missed in the post.
Check your source and then edit the post.
Then re-submit.
The logic behind this problem is THIS:
Let the bag costs C pesos.
Then, according to the condition,
Anmy has (C-200) pesos;
Brian has (C-2400) pesos;
Together, they have (2C-2600) pesos,
and it is still not enough, i.e. 2C-2600 < C. (*)
From this inequality, you only can say that C < 2600.
You can also add that C > 2400.
So, the compound inequality 2400 < C < 2600 is ALL that we can extract from this condition.
Had the condition says, instead of (*), how much they are short together, then it would create an additional equation
to solve the problem by an unique way.
So, again, the condition is INCORRECT and requires to be corrected.