Solving systems of equations by substitution

The substitution is one of the way to sovle the equation. During the substitution, there are several rules,which are:

1 Express one of equation in terms of the variable in the other equation

2 Obtain an equation in one variable equation by combining the two equations

3 Solve the new equation

4 Substitute the solution in step3, to find the other variable

5 Check by substituting answers into the originial equations