I'm assuming you mean "how many pounds of Gala apples does she have left?" I'm also gonna include the solution on how many apples she has left in total.
So we know that she had 4 pounds, and used 1 3/4. So we subtract 1 3/4 from 4:
4 - 1 3/4 = 2 1/4.
To find the total amount of apples, you add 2 1/4 by 3 1/2 (or 3 2/4):
2 1/4 + 3 2/4 = 5 3/4
Amount of Gala apples left: 2 1/4 pounds.
Total amount of apples: 5 3/4 pounds.
