To find out what fraction of his M&M's Max should eat, we first need to determine the fraction of M&M's that Emma ate.
Emma started with 6 M&M's and ate 4 of them. The fraction that Emma ate is:
\[ \text{Fraction Emma ate} = \frac{\text{M&M's eaten}}{\text{Total M&M's}} = \frac{4}{6} = \frac{2}{3} \]
Now, Max wants to eat the same fraction of his M&M's. Max starts with 3 M&M's. The fraction of M&M's that Max should eat is also \(\frac{2}{3}\).
Therefore, Max should eat:
\[ \text{Fraction of Max's M&M's to eat} = \frac{2}{3} \]
The correct answer is:
2 thirds.