When a number is decreased by 17% the result is 15. what is the original number?

original number is 18.07

Step-by-step explanation:

Let the original number be x

x - 17% of x = 15

x * (1 - 0.17) = 15

x * 0.83 = 15

x = 15/0.83

x = 18.072289156

Or if your wording meant 17% of a number is 15 then:

x * 17% = 15

x * 0.17 = 15

x = 15/0.17 = 88.23529 ...

but I think you meant "decreased by 17%" so I choose x = 18.07