In its simplest form, an equation is represented by expressions written with an equal sign in between; the two entities on either side are equal to each other. They are among the simplest mathematical problems most people deal with; in fact, most people have solved equations in their daily lives without realizing it. For example, when students first learned addition in school, they typically work on equations such as: ____ + 5 = 7, in which the blank needs to be filled. This problem could also be expressed as x + 5 = 7, a simple equation. In this case, the equation is solved when x equals 2. The following are also equations:

6 = 6

x = 8

y + 8 = 14

x - 4 - 15 - x

5xy - 8xy² + 4

There are also some fundamental properties of equations that are good to know. They include symmetric properties (if a = b, then b = a); substitution (if a = b, then a may be replaced by b); addition (if a = b, and c is a number, then a + c = b + c); and multiplication (if a = b, and c is a number, then a × c = b × c).