Answer 1

Here is a revision of your original work.

#include <iostream>
using namespace std;

int main()
{
int age = 43;

cout << "Enter your age: "; cin >> age;

if (age < 3 && age >= 1) cout << "Toddler";
else if (age < 5 && age >= 3) cout << "Preschooler";
else if (age < 12 && age >= 5) cout << "Gradeschooler";
else if (age < 18 && age >= 12) cout << "Teen";
else if (age < 43 && age >= 18) cout << "Adult";
else if (age < 70 && age >= 43) cout << "Senior";
else cout << "The age is uncategorized.";
}

As you see, if...else statement is more fit for your problem.