Sum of a number and it's reciprocal is 6. What is the number?

Let the number be n.
The reciprocal is 1/n.

The word is means an equation, so we set n + 1/n equal to 6
n + 1/n = 6

Multiply each side by n to remove the fraction:
n^2 + 1 = 6n

Subtract 6n from each side:
n^2 - 6n + 1 = 0 <-- This is our algebraic expression

If the problem asks you to solve for n, then you type this quadratic equation into our search engine.