Learn all about how to solve for X in one-step and two-step equations with addition, subtraction, multiplication and division.  X stands for an unknown value or a variable and was first used by ancient Greek mathematicians. Euclid of ancient Greece demonstrated mathematical concepts such as the distributive property. Ancient Indian, Chinese and Persian mathematicians also contributed to algebra methods. We learn how to solve for an unknown value or variable in an equation, and what to do if there is a fraction or a decimal as a coefficient with X. Exciting video and dynamic graphics reinforce important concepts.