If the recipe calls for 2/3 of a cup of sugar for every 2 cups of flour, then the ratio of sugar to flour is 2/3 : 2 or 2:9.
To find out how much sugar you need when using 1.5 cups of flour, we can set up a proportion:
2/9 = x/1.5
Cross-multiplying, we get:
2(1.5) = 9x
3 = 9x
x = 3/9
x = 1/3
Therefore, you will need 1/3 of a cup of sugar when using 1.5 cups of flour in this recipe.