We can translate this question directly into symbols. Even though this one is simple enough that we can probably intuit the answer without writing it out, it is good practice for when you're faced with a problem that is more complex. It's also good practice for writing things in general. We've noticed that your handwriting has gotten a little sloppy as of late. Our unknown number is *x* and we are averaging two numbers, so $$\frac{5 + x}{2} = 9$$ Solving this equation gives us *x* = 13. |