A pizza shop charges $9 for a large cheese pizza. Additional toppings cost$1.25 per topping. Heather paid $15.25 for her large pizza. How many toppings did she order?

Let T be the number of toppings Heather ordered.

Her total cost is 9 + 1.25T dollars.
Thus, 9 + 1.25T = 15.25.
Therefore, 1.25T = 6.25.
Hence, the number of toppings she ordered is T = 6.25 / 1.25 = <<6.25/1.25=5>>5. Answer: \boxed{5}.