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# Isn't that a Double? why it said it's not a Double?

Isn't that a Double? why it said it's not a Double?

struct.swift
```struct Expense {
var description: String
var amount: Double = 0.0

init (description: String) {
self.description = description
}
func calculateTaxes(percentage: Double) -> Double? {
return self.amount*(percentage/100)
// add the calculateTaxes method here
// it should accept only one parameter named 'percentage' of type Double
}
}

var item = Expense(description: "myke")
item.amount = 100
var taxes = item.calculateTaxes(7.5)
```

Hello Ling:

Your code looks perfect, Iโm not sure why is not passing your challenge. I just finished the challenge myself to see what is wrong but canโt seem to find a difference between mine and yours, other than a few spaces that should not affect anything. Anyways here is my code if you want to check yours and see if you can fix it.

```struct Expense {
var description: String
var amount: Double = 0.0

init (description: String) {
self.description = description
}

// add the calculateTaxes method here
func calculateTaxes(percentage: Double) -> Double {
return self.amount * (percentage / 100)
}
// it should accept only one parameter named 'percentage' of type Double
}

var item = Expense(description: "Nike")
item.amount = 100
var taxes = item.calculateTaxes(7.5)
```

I've found that out, my Double is an optional that makes me couldn't get through this.

Thnaks!!