Let's break down the problem step by step:

1. Papa bear ate half of the pie, meaning after Papa bear, half the pie (or $\frac{1}{2}$) is left.

2. Mama bear ate half of what was left, which means she ate half of the remaining $\frac{1}{2}$ of the pie. So, Mama bear ate $\frac{1}{2} \times \frac{1}{2} = \frac{1}{4}$ of the whole pie. After Mama bear, $\frac{1}{2} - \frac{1}{4} = \frac{1}{4}$ of the pie remains.

3. Baby bear ate half of what was left after Mama bear finished eating, meaning Baby bear ate half of $\frac{1}{4}$, which is $\frac{1}{2} \times \frac{1}{4} = \frac{1}{8}$.

4. What is left for Goldilocks is the remaining fraction of the pie after all the bears have eaten. That is: $\text{Remaining pie} = \frac{1}{4} - \frac{1}{8} = \frac{2}{8} - \frac{1}{8} = \frac{1}{8}$

So, Goldilocks has $\frac{1}{8}$ of the pie left.

Would you like further details on any part of this solution?

Here are 5 questions to expand your understanding:

1. If Papa bear ate $\frac{2}{3}$ of the pie instead of half, how much would be left for Goldilocks?
2. What fraction of the pie did all the bears eat together?
3. How would the problem change if Baby bear ate two-thirds of what was left after Mama bear ate?
4. Can you express the amount of pie left for Goldilocks as a decimal?
5. If Mama bear ate three-quarters of what Papa bear left, how much would remain for Goldilocks?

Tip: Always keep track of portions as fractions when solving problems involving multiple reductions or divisions.