# How do you use this symbol in an equation? in

See below:

#### Explanation:

The symbol $\in$ means that something (called an element) lies within a set.

For instance, I can use it to say something like *within the set of rooms in my house, there is a kitchen, which I can write as:

"kitchen"in {"rooms in my house"}

While the symbol $\in$ shows up for set operations, we can use it for other things. For instance, let's say we want to create an equation where the value(s) we're putting in need to be a certain type of value.

For instance, what if I want to have an equation that tells me how much it will cost to talk to a lawyer. The lawyer charges $100/hour, and so I can write: "Cost of lawyer"="number of hours" xx$100

and I can add some symbols and write it as :

C=$100h We don't want to deal with fractional hours - we only want the natural numbers, so to limit the type of number we substitute in for $h$, we can say: C=$100h; h in NN