This site gives a nice review of solving simple systems of equations.
http://www.purplemath.com/modules/systlin1.htm
This site gives a review of solving simple systems of equations by adding with links to solving simple systems using other methods. This is a great site if you take this link along with the other links provided at this site.
http://www.analyzemath.com/Tutorial-System-Equations/Tutorial-System-Equations.html
Here is a site for solving systems of equations by graphing.
You need to solve the first equation for y and enter the result on the line called f1(x), and then solve the second equation for y and enter the result on the line called f2(x). Finally, look for the point of intersection.
https://www.symbolab.com/solver/conic-sections-calculator