Chapter 1 - Foundations for Algebra - 1-1 Variables and Expressions - Practice and Problem-Solving Exercises - Page 8: 40

$150+(2.00\times n)$

Since the salesperson earns 2.00 for every shoe he sells, the variable n can represents the number of shoes sold and since he earns a weekly salary of 150, we will add that to the total the salesperson will earn. We could also rewrite the formula in a more algebraic way as $2n + 150$