Answer:
system of equations: set of one or more equations involving a number of variables
substitution method:
1. Solve one equation for one of the variables.
2. Substitute (plug-in) this expression into the other equation and solve.
3. Resubstitute the value into the original equation to find the corresponding variable.
ex:
-4x+3y=-2 y=x-1
plug in: -4x+3(x-1)=-2
simplify: -x-3=-2
-x=-2+3
-x=1
answer: x=1