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# why do these things never work!!!

I know this is right and have tested it in a playground.. wasting hours.. please fix this

/** For this code challenge, let’s define a math operation as a function that carries out some work on two integers and returns an integer as well. An example is the function below, `differenceBetweenNumbers`, which takes two integers and calculates the difference between the numbers. After calculating, it returns the difference. */

func differenceBetweenNumbers(a: Int, b:Int) -> (Int) { return a - b }

// Enter your code below func mathOperation(mathOp: (Int, Int) -> Int, a: Int, b: Int) -> (Int) { return mathOp(a, b) }

let difference = mathOperation(differenceBetweenNumbers, 10, 20)

higherOrderFunctions.swift
```/**
For this code challenge, let’s define a math operation as a function that
carries out some work on two integers and returns an integer as well. An
example is the function below, `differenceBetweenNumbers`, which takes two
integers and calculates the difference between the numbers. After calculating,
it returns the difference.
*/

func differenceBetweenNumbers(a: Int, b:Int) -> (Int) {
return a - b
}

func mathOperation(mathOp: (Int, Int) -> Int, a: Int, b: Int) -> (Int) {
return mathOp(a, b)
}

let difference = mathOperation(differenceBetweenNumbers, 10, 20)
``` Same here. It would be nice to know why the code above is not considered correct. Here is my code, just for the records. It is (basically) the same as @scottharris4

```func mathOperation(mathOp:(Int, Int) -> (Int), a: Int, b: Int) -> Int {
return mathOp(a, b)
}

let difference = mathOperation(differenceBetweenNumbers, 10, 8)
``` I think in this particular case it is just the code check. Others had the same problems, although the code works as expected in playground. It seems that removing the parenthesis from the `mathOperation` return type does the trick. Change your code from

```-> (Int)
```

to

```-> Int
```

So again, it wasn't a mistake you made ;)