Swift How to add random math symbol

How I can get random math symbol from array and change the type from string?? and then use in my code? its giving me error because I used it as string in xxl valuable

let arr = [1, 2, 3, 4, 5, 6, 7, 8, 9]
let arr1 = ["+", "-", "*"]

for _ in 1...100{
    let x = 0
    if x < 100{
        var aa = arr1.randomElement()
        var bb = arr1.randomElement()
        var cc = arr1.randomElement()
        var dd = arr1.randomElement()
        var ee = arr1.randomElement()
        var ff = arr1.randomElement()
        var gg = arr1.randomElement()
        var hh = arr1.randomElement()
        var a1 = arr[0]
        var a2 = arr[1]
        var a3 = arr[2]
        var a4 = arr[3]
        var a5 = arr[4]
        var a6 = arr[5]
        var a7 = arr[6]
        var a8 = arr[7]
        var a9 = arr[8]
        var xxl = a1 + aa + a2 + bb + a3 + cc + a4 + dd + a5 + ee + a6 + ff + a7 + gg + a8 + hh + a9
        print("OMG symbol is \(xxl)")
    }else{
        print(x)
    }
}