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Math definition of Substitution: Substitution - A strategy for solving systems of equations that include solving for one variable and using that solution to find the other variable. 1  Subject : Math.  Topic : Algebra 2.
The goal of the substitution method is to completely eliminate one of the two variables in the linear system by replacing it with an equivalent expression. This goal is accomplished by solving for one variable from one equation and plugging it into the other equation.