Aiden had $\frac{3}{5}$ of an apple pie. He gave $\frac{3}{4}$ of what he had to Brianna. To find out what fraction of the whole pie Brianna received, we multiply the fraction Aiden had by the fraction he gave to Brianna:

$\frac{3}{5} \times \frac{3}{4} = \frac{3 \times 3}{5 \times 4} = \frac{9}{20}$

So, Brianna received $\frac{9}{20}$ of the whole pie.

Would you like further clarification or details?

Here are 5 related questions:

1. If Aiden had 2/3 of the pie instead, how much would Brianna have received?
2. What fraction of the pie did Aiden have left after giving some to Brianna?
3. If Brianna had shared her pie with another friend, giving away 1/2 of her portion, how much of the whole pie would her friend get?
4. How much pie would Aiden need to give Brianna for her to have 1/2 of the whole pie?
5. What percentage of the whole pie did Brianna receive?

Tip: When multiplying fractions, simply multiply the numerators and denominators, then simplify if possible.