Precalculus (Algebra + Trigonometry) Stewart Precalculus – Chapter 1- Fundamentals: Properties of Real Numbers | State the property of real numbers being used. (x+2y)+3z=x+(2y+3z). This is a preview of this lesson for those interested in joining PLEM Academy by Jonathan David. Membership Required You must be a member to access this content.View Membership LevelsAlready a member? Log in here