The elimination method is used for solving linear systems of equations.It is way of solving a linear system of equations.In the elimination method we either add or subtract the equations to get an equation in one variable.The main concept behind elimination method is to create terms with opposite coefficients because they cancel each other when added.
When the coefficients of one variable are opposites you add the equations to eliminate a variable and when the coefficients of one variable are equal you subtract the equations to eliminate a variable.
When Heather has to solve this system of equations using elimination her first step will be to make the coefficients of x or y the same so that one of the variable is eliminated on addition or subtraction of the equations.