Answer:
This depends on the situation. For context, you use less than when your inequality CANNOT exceed more than.
You would use less than or equal to if your inequality can be equal to a number. Here's an example.
John needs to buy X oranges and Y apples. He can AT MOST buy 10 total fruits.
x + y (equal to or less than) 45
John needs to buy X oranges and Y apples. He CANNOT buy more than 10 total fruits.
x + y < 45