|Substitution Property of Equality|
If the values of two quantities are known to be equal, you can replace the value of one quantity with the other.
For example, take the following equation with variables x and y:
2x + 7y = ?
If we know that x = 3, and y = 1, we can replace the variables in the equation with those values, and then solve the equation.
2(3) + 7(1) = 13