Not Enough Money

Let $B$ be the cost of the banana, and note that the sum of their money is $(B-2) + (B-24) = 2B-26.$ Since they can't afford the banana together, $2B-26 < B$ which is equivalent to $B < 26.$ However, since Brian is 24 pennies short, $B>24.$ Thus, $B=25.$

From intuition, the answer will be 24 or 25. If we ignore 24 as it makes brian penniless, we get 25.

Banana = Amy + 2.
Banana = Brian + 24.
Banana > Amy + Brian.

Thus, Banana > (Banana - 2) + (Banana - 24) $\Rightarrow$ Banana > 2Banana - 26.
Therefore, Banana < 26.

Since Brian is 24 short, and assuming he has at least one penny, then Banana > 24.
So 24 < Banana < 26, which leaves 25 as the only possible integer.
So Banana = 25, Amy = 23, Brian = 1, and Amy + Brian = 24 which is < Banana.

The solution of this question requires creation of a linear inequation. Let the cost of the article be x. A is 2 pennies short : x-2. B is 24 pennies short : x-24. Now, Even the combination, that is (x-2+x-24), is not sufficient Thus,

x-2+x-24<x

2x-26<x

x<26

Therefore the maximum possible answer is 1 integer less than 26, that is 25.

Brian being 24p short means B is greater than 24p, but Amy and Brian's money is 2B - 26p, which is less than B, so B is less than 26p. Combining these points means B = 25p