Bobby has a bag containing 2 sizes of marbles. The big ones weigh 6 g and the small ones weigh 4 g. If there are an equal number of small ones and big ones and the bag weighs 220 g, how many big marbles does he have?

Question

anonymous · Answer

put the number of 6g marbles as $x$ and so since there are equal amount of 6 and 4g marbles, the number of 4g marbles is also $x$
therefore the total weight is given by 
$$6x+4x=220$$ 
solve for $x$

anonymous · Answer

figured it out off this! thanks its super easy when you write it out this way. just add the x's and divide