If $latex xy = 120 &s=1$ and $latex y = 15 &s=1$, then $latex y-x= &s=1$

1. 5 (check answer)
2. 7 (check answer)
3. 8 (check answer)
4. 12 (check answer)
5. 15 (check answer)

Solutions, hints, and questions are welcomed. A full solution will be posted on the August 31st. If you would like to learn how to enter math formulas into this blog, visit the WordPress LaTeX tutorial page.