A letter that represents an unspecified number is called a variable. To evaluate expressions of algebra, we need to substitute a number of each of the variables in the equation and perform the arithmetic operation. Suppose, we have x + 10 = 20. Here, x will be equal to 10, since 10 + 10 = 20. Once we know the value of the variables in any given equation, we can substitute the variable with their actual values and then evaluate the expression.

Grade 6

Expressions, Equations, And Inequalities

6.EE.A.2.C