To determine how many cups of almonds Luis will need for 3 cups of chocolate chips, we start with the ratio given in the recipe. The recipe indicates that for every 3/4 cup of chocolate chips, 1/8 cup of almonds is required.
First, we find out how many times 3/4 cups go into 3 cups of chocolate chips:
\[ 3 \text{ cups} \div \frac{3}{4} \text{ cups} = 3 \times \frac{4}{3} = 4 \]
This means that 3 cups of chocolate chips is equivalent to 4 portions of 3/4 cups.
Next, since each portion requires 1/8 cup of almonds, we multiply the number of portions (4) by the amount of almonds needed for each portion (1/8 cup):
\[ 4 \times \frac{1}{8} \text{ cup} = \frac{4}{8} \text{ cup} = \frac{1}{2} \text{ cup} \]
Therefore, Luis will need 1/2 cup of almonds for 3 cups of chocolate chips.