Before substitution is possible, one equation must have an isolated variable. Notice that by adding to both sides of Equation (I), can be isolated.
Substitute the rewritten equation from Step into the other equation by substituting the expression equal to in Equation (II). Now, Equation (II) only has one variable,
The sum of two numbers is One of the numbers is two more than three times the other number. Write a system that represents the given relationships. Then, find the numbers using substitution.
We can use the given information to write two equations. First, we must define our variables. Let the first number be and the other We know that the sum of these numbers is Thus, We also know that one of the numbers, let's say is two more than three times the other number, which is then This gives us the equation Together these two equations create the system To solve this system using substitution, we must substitute one equation into the other. Let's substitute into This will allow us to then solve for