A machine that produces silicon bottle stoppers, makes 36 stoppers weighing 6y grams each, and 9x stoppers weighing 12 grams each. What is the average weight (arithmetic mean) per stopper?  Choose the correct choice from the following options.
A) (36y + 18x)/(y + 2)
B) (18y + 9x)/4
C) (36x)/(2y + 3x)
D) (24y + 12x)/(4 + x)
E) 6 + 3y
The total number silicon stoppers weighing 6y grams is 36 and 12 grams is 9x   Average weight = (36*6y + 9x*12)/36+9x   = (9(24x + 12y))/(9(4+x))   = 24x+12y/4+x   (Option (24y + 12x)/(4 + x))
<result>D</result>
A machine that produces silicon bottle stoppers, makes 36 stoppers weighing 6y grams each, and 9x stoppers weighing 12 grams each. What is the average weight (arithmetic mean) per stopper?