To find out how many pens Tatum puts into each cup, we first need to determine the total number of pens he has after opening the packages.
Tatum opens 6 packages, and each package contains 4 pens. Thus, the total number of pens is calculated as follows:
\[ \text{Total pens} = \text{Number of packages} \times \text{Pens per package} = 6 \times 4 = 24 \]
Now that we know Tatum has 24 pens, we need to divide these pens equally into 3 cups:
\[ \text{Pens per cup} = \frac{\text{Total pens}}{\text{Number of cups}} = \frac{24}{3} = 8 \]
Therefore, Tatum puts 8 pens into each cup.