How can i solve , what is 10% of 55?

50 points~ ! i have to turn this in tomarrow

Marquise has 200 meters of fencing to build a rectangular garden. the garden's area (in square meters) as a function of the garden's width w w (in meters) is modeled by: a ( w ) = − w 2 + 1 0 0 w a(w)=−w 2 +100w what side width will produce the maximum garden area? meters

Write the percent as a fraction or mixed number in simplest form. 0.8%