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The solution in the post by @mananth is inconsistent with the problem
and therefore is incorrect and irrelevant.
I came to bring a correct solution.
In accordance with the problem's logic, you should combine 3 egg tarts at $1.60 with 2 egg tarts at $1.30
and do it as many times until the restriction of $24.00 allows you do it.
Each such elementary group costs 3*1.60 + 2*1.30 = 7.40 dollars.
Next you divide 24 by 7.40 and round it to have integer quotient.
Obviously, this integer quotient is 3; so, you may have 3 elementary groups
that cost 7.40*3 = 22.20 dollars,
leaving 24.00 - 22.20 = 1.80 dollars.
For this $1.80, you can buy one egg tart at $1.60.
So, at the end, you will have maximum (3*(3+2) + 1) = 3*5+1 = 16 egg tarts and $0.20 remaining in your pocket.
Solved.
Actually, it is quite primitive task/problem/assignment.
The solution is straightforward and does not require "mind game".
Any house-wife can solve it mentally, based on common sense,
even without having any mathematical education.
One similar problem was solved for you today by Edwin.