void setup() {
  Serial.begin(9600);
  Serial.println(" ");//no need
}

void loop() {
  digitalWrite(13, LOW);
  if (Serial.available()) {
    int num1 = Serial.parseInt();
    int num2 = Serial.parseInt();
    Serial.read();
    Serial.println(String(num1) + "+" + String(num2) + "=" + String(num1 + num2)); //plus
    Serial.println(String(num1) + "-" + String(num2) + "=" + String(num1 - num2)); //minus
    Serial.println(String(num1) + "*" + String(num2) + "=" + String(num1 * num2)); //multi
  }
}