The Division Property of Equality lets you divide both sides of an equation by any number except which one?

1. Dividing both sides of an equation by the same quantity keeps the two sides equal. 2. The one exception is zero, because division by zero is undefined. 3. So both sides may be divided by any non-zero number, and only zero is ruled out. 4. Negative numbers, fractions, and one are all fine to divide by; dividing by one just leaves the equation unchanged. _Source: OpenStax Elementary Algebra (CC BY 4.0), Ch 2 "Solving Linear Equations and Inequalities", section 2.2 Solve Equations using the Division and Multiplication Properties of Equality_