This site will help you with answers like this!
http://www.geteasysolution.com/5x+2y=7
Answer:
A time when they are green, a time when they're brown, but both of these times, cause me to frown. But just in between, for a very short while, They're perfect and yellow and cause me to smile!
What am I talking about here?
Flossing, brushing twice a day and stuff