@IBAction func operationButtons(_ sender: UIButton) { if resultLabel.text != "" && sender.tag != 11 && sender.tag != 17{ firstNumber = Double(resultLabel.text!)! if sender.tag == 12 { //% resultLabel.text = "%" } else if sender.tag == 13 { // / resultLabel.text = "/" } else if sender.tag == 14 { // * resultLabel.text = "X" } else if sender.tag == 15 { // - resultLabel.text = "-" } else if sender.tag == 16 { // + resultLabel.text = "+" } operation = sender.tag isMath = true } else if sender.tag == 11{ firstNumber = 0 nextNumber = 0 operation = 0 resultLabel.text = "" } else if sender.tag == 17{ if operation == 12 { resultLabel.text = String(firstNumber / 100) } else if operation == 13 { resultLabel.text = String(firstNumber / nextNumber) } else if operation == 14 { resultLabel.text = String(firstNumber * nextNumber) } else if operation == 15 { resultLabel.text = String(firstNumber - nextNumber) } else if operation == 16 { resultLabel.text = String(firstNumber + nextNumber) } } }