Students will learn how to evaluate expressions by first substituting two or more variables with their values. Variables may have values of integers, rationals, or decimal numbers.

TODO: When do we substitute variables with expressions? For example, if \(z = y + 1,\) \(y = 2x\) and \(x = 3,\) then \(y = 2 \cdot 3 = 6\) and \(z = 6 + 1 = 7.\)