void setup() {
  Serial.begin(9600);
}

void loop() {
  Serial.println("Enter 1-Adult or 2-Child");
  while (Serial.available() == 0);
  int age = Serial.parseInt();

  Serial.println("How many books were loaned?");
  while (Serial.available() == 0);
  int loaned = Serial.parseInt();

  Serial.println("How long do you hold a book");
  while (Serial.available() == 0);
  int bookAtHome = Serial.parseInt();

  if (bookAtHome > 30) {
    Serial.println("You can not loan a book");
  }
  else {
    if (age == 1 && (5 - loaned) > 0) {
      Serial.println("You can loan a book");
    }
    if (age == 1 && (5 - loaned) == 0) {
      Serial.println("You can not loan a book");
    }
    if (age == 2 && (3 - loaned) > 0) {
      Serial.println("You can loan a book");
    }
    if (age == 2 && (3 - loaned) == 0) {
      Serial.println("You can not loan a book");
    }

  }
}