I've been asked to write an algebraic expression for the perimeter of a hexagon. O.K. I've assigned "n" to represent the length of a single side and I think my expression is n6. Am I corrent?

That will work, although p=6s would be a better form where p=perimeter and s is the length of a side.

n in math usually denotes the number of objects and constants are usually used before variables hence 6n is preferred over n6.

Although, you could write a perimeter eqn from knowing the diameter of the smallest circle that would fit outside of the hexagon. It's more trouble than it's worth, but is similar to a circle which uses radius and diameter. I think it's safe to come up with the simplest eqn.