Let y = the number of volleyballs
You can't make a negative number of balls, so you're first two constraints would be:
You're going to be cutting and sewing, so it makes sense to find out how much time it takes to cut and sew one soccer ball and one volleyball.
Let's start with cutting
If it takes 2 hours of cutting to make 75 soccer balls (SB), how many hours of cutting does it take to make 1 soccer ball?
75 SB in 2 hrs means 1 SB in hrs.
Use similar logic to determine how long it takes to cut one volleyball (VB).
60 VB in 3 hrs means 1 VB in hrs.
The limitation on cutting hours is 500 hours. Now you can set up your third constraint,
Now, go work on the sewing part to come up with your 4th and final constraint. Use the same logic as with cutting.