Solution: Filter with Less Than

db.pets.find(
    {
        sex: "male",
        type: "dog"
    }
)

db.pets.find(
    {
        sex: "male"
    }
).count();



db.pets.find(
    {
        age: { $lte: 4}
    }
)

db.pets.find(
    {
        age: { $lte: 4}
    }
).count();

db.pets.find(
    {
        age: { $lt: 4}
    }
)

db.pets.find(
    {
        age: { $lt: 4}
    }
).count();