The box can be replaced by another symbol such as . The value of the box in the first equation and that of the triangle in the second equation is 8. The box, triangle, and blank are variables . A letter such as x is often used as a variable. In an equation, the equals sign indicates that the quantities on each side of the sign must be equal.
Students can think of an equation as a balance, with the equals sign as the balance point.
Both sides of the balance must equal the same thing at all times for the pans to balance. Notice that the scales above are balanced because each pan has a five on it. Now look at the next figure. This scale is also balanced, because the total on each side is 5. It is important to understand that we want to keep the pans balanced.