To find the number of cups of almonds Luis will need, we can set up a proportion using the relationship given in the recipe.
Let "x" represent the number of cups of almonds Luis will need.
Using the proportion:
18/34 = x/3
Cross multiplying, we get:
34x = 3 * 18
34x = 54
x = 54/34
x ≈ 1.588
Rounding to the nearest tenth, Luis will need approximately 1.6 cups of almonds.