To find out how many cups of almonds Luis will need for 3 cups of chocolate chips, we start with the ratio provided in the recipe:
For every \( \frac{3}{4} \) cup of chocolate chips, \( \frac{1}{8} \) cup of almonds is required.
Let's first determine how many times \( \frac{3}{4} \) fits into 3 cups:
\[ 3 \div \frac{3}{4} = 3 \times \frac{4}{3} = 4 \]
This means that 3 cups of chocolate chips is equivalent to 4 times \( \frac{3}{4} \) cups.
Now, since we need \( \frac{1}{8} \) cup of almonds for each \( \frac{3}{4} \) cup of chocolate chips, we multiply the amount of almonds by 4:
\[ \text{Almonds required} = 4 \times \frac{1}{8} = \frac{4}{8} = \frac{1}{2} \]
Thus, Luis will need \( \frac{1}{2} \) cup of almonds.
Rounding to the nearest tenth, the answer is:
0.5 cup.