1. Q Essential Question When is substitution a useful method for solving systems of equations? In 4.

## Step 1<br />Substitution is a method used to solve systems of equations. This method is particularly useful when one of the equations is already solved for one variable. This means that one of the equations is in the form \(y = \text{something}\) or \(x = \text{something}\).<br /><br />## Step 2<br />When this is the case, you can substitute the expression for that variable into the other equation. This will then give you an equation with only one variable, which you can solve.<br /><br />## Step 3<br />Once you have the value of one variable, you can substitute it back into one of the original equations to find the value of the other variable.<br /><br />## Step 4<br />This method is especially useful when the system of equations is linear and consists of two equations in two variables. However, it can also be applied to systems of equations with more variables.