When using substitution to solve equations, what is the first step?

Using substitution to solve equations involves expressing one variable in terms of another variable and then using this relationship to replace that variable in the other equation. The first step in the substitution method is to express one variable in terms of the other. This enables you to take the value of one variable and substitute it into another equation, making it possible to solve for the remaining variable.

This method is particularly useful when dealing with systems of equations, where you often have two or more equations involving multiple variables. By defining one variable in terms of another, you simplify the system into a single equation with one variable, which can be easily solved.

In this context, combining like terms, isolating one variable on one side, or applying the quadratic formula would come later in the problem-solving process, depending on the specific equations you are working with. These steps, while important in certain circumstances, do not represent the initial action taken when employing substitution.