Negative numbers are numbers less than zero. The thing I didn't understand when I was younger was that -1 is greater than -200. I thought, Isn't 200 greater than 1? Later, I realized by using number lines that the numbers go backwards until they reach zero. Then, they go in order like they should be. 
     An example of how we use negative numbers is in your bank account. A check will bounce if you already have no money in your account. Negative cash can be a problem. Even if it isn't your bank account. Most of us kids don't have credit cards. Some have a savings account to save for college funds, but not a real credit card like adults do. I have a prepaid card, but it's not the same. Us kids will probably have a more likely chance that we owe money to other people because they bought us something, you lost a bet, and many, many other reasons. 

     The equation above is quite simple to solve. It's pretty basic math. The main idea to this problem is to isolate the variable. In this case, the variable is "x". In other words, we need to get "x" by itself.