Solving Systems of Equations by Substitution

Please use the applet to practice using the substitution technique. However, the computer cannot tell how you found your answers: if you think that you need more practice using elimination, feel free to use that instead to solve the system. Also, numbers are randomly generated, so your answers will MOST LIKELY be UGLY FRACTIONS. This is OK: please do your best, and trust in your skills. If necessary, use a calculator.
How many can you get right in a row?