Math Medics
S.o.s. Math: Order of Operations
This lesson contains four rules on order of operations and several examples of each. It also allows you to work out practice problems.
AAA Math
Aaa Math: Properties of Addition
Explains the four mathematic properties of addition. Gives exercises and games to practice this skill.
Washington State University
Washington State University: Order of Operations
Washington State University provides a short lesson concerning which operations to execute first in solving an equation. The site provides the answers with an example.