Answer:
Hisaki can make 4 2/3 batches of cookies with 3 1/2 cups of sugar. 
Explanation:
Let x be number of batches with 3.5 cups. (I've converted the fractions to decimals to simply calculation. Let me know if you want an explanation where I retain the fractions as-is.)
1 batch = 0.75 cup
 x batches = 3.5 cups 
-using unitary method- 
( 3.5 * 1 ) / 0.75 = x 
4.66667 = x 
Therefore, number of batches = x = 4 2/3 batches.