OK, Math Superstars! We can help the police chief crack the code of that Presto Function Changer. We
just need to find the FUNCTION the Phantom is using to change the town's numbers. First, we need to
understand what a function is:

A function is an expression that involves either adding, subtracting, multiplying, or dividing any given
number. I'll represent that number with the letter n. An example of a simple function with the number n
would be n+3.

Some functions can involve all four operations or combinations of operations. For example, another
function with the number n may be 2n+1. To see how this works, let's substitute 2 for n. We now have
2(2)+1, or 4+1, or 5. That means if the Phantom Number Cruncher was using the function 2n+1, every 2
in town would become a 5!

Now we know how to change numbers using a given function. But our job is going to be a bit trickier,
because we have to use the old numbers and the new numbers to find the function that changed them!

Which of the following functions is that tricky Phantom using to change all the numbers in town? (Hint: n
represents the original numbers.)