Final answer:
In 3-variable substitution, look for a variable that can be isolated, simplifies the equation, and appears in multiple equations.
Step-by-step explanation:
In 3-variable substitution, when selecting a variable to solve for, there are a few things to look for that would make one variable easier to work with than the others.
1. Isolation: Look for a variable that can be isolated on one side of an equation, so it can easily be solved for. This means that the other variables in the equation should be known.
Simplification: Choose a variable that, when solved for, will simplify the equation or system of equations.
Consistency: If possible, choose a variable that appears in more than one equation. This can lead to a more consistent solution.