# Two-Step Equations with Addition and Multiplication

## Two-step equations ax + b = c

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Practice Two-Step Equations with Addition and Multiplication

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A Chemical Balance

Credit: U.S. Army
Source: http://www.flickr.com/photos/rdecom/8050389566/
License: CC BY-NC 3.0

Do you know what a chemical equation is? A chemical equation is a symbolic representation of a chemical reaction. Elements are written in a particular order, with the reactant elements on the left side and the products of these combinations on the right side. Chemists work with chemical equations all the time.

#### Why It Matters

Chemical equations have to be balanced. In order to balance a chemical equation, you must have the same number of atoms of each element on both sides of the equation.

Credit: Laura Guerin
Source: CK-12 Foundation
License: CC BY-NC 3.0

What does this mean? It means that you might need to rearrange the proportions of reactants and products to balance a chemical equation. If you add elements to the left side of the equation, this increase must also be applied to the right side—and vice versa. In this way, we can find and maintain the "chemical balance." If you look at the example depicted above, you can see that the coefficients of O2 and H2O were increased to 2 in order to balance the equation. As a result, there are equal amounts of each element on each side of the equation: 1 carbon (C), 4 hydrogen (H), and 4 oxygen (O) atoms.

See some chemical reactions in action: http://www.youtube.com/watch?v=8TPnns-5UxA

#### Explore More

Check out the first two links for interactive activities that will help you visualize the importance of keeping both sides of an equation "balanced" as you solve it. Play the math basketball game at the next link to practice solving one-step equations.

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