1. The problem statement, all variables and given/known data Find all x for which 2x < 8 (where x is a natural number). 2. Relevant equations Those pesky 12 properties. 3. The attempt at a solution This could be done by simply testing values of x, but that approach is not very scalable. What is the correct way to start this (using only the basic properties of numbers)? What is Spivak looking for? Thanks.