Mathematics

# a drawer has some red ,green and blue marbles.there are 33 marbles . there are 4 times as many red marbles as green marbles.there are half as many blue marbles as green marbles. how many blue marbles are in the drawer?

$g-green\ marbles\\r-red\ marbles\\b-blue\ marbles\\g+r+b=33\\\\4g-red\ marbles\\\frac{1}{2}g-blue\ marbles\\\\g+4g+\frac{1}{2}g=33\\\\5\frac{1}{2}g=33\\\\\frac{11}{2}g=33\ \ \ \ /\cdot\frac{2}{11}\\\\g=3\\\\Answer:b=\frac{1}{2}g\to b=\frac{1}{2}\cdot6=3$