while counter < numbers.count { sum += numbers(counter) counter += 1 } what am I not doing right, been hours

while counter < numbers.count { sum += numbers(counter) counter += 1 }

I am not sure why this is not working, please help me get past this, even on Xcode I cannot seem to pull items from my array when it comes to this while loop, it shows up blank, or says it can't convert type INT, really stuck

let numbers = [2,8,1,16,4,3,9]
var sum = 0
var counter = 0

// Enter your code below

while counter < numbers.count {
  sum += numbers(counter)
  counter += 1
}