int X = 10;
int Y = 5;
int Dt = 500;
String operador = "+";
String igual = "=";




void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
}

void loop() {
  // put your main code here, to run repeatedly:
int Z = X * Y;
Serial.print(X);
Serial.print(operador);
Serial.print(Y);
Serial.print(igual);
Serial.println(Z);
delay(Dt);
X = Z;  
}