how to write an equation, choosing a variable for the unknown for this problem. mary bought some used cds for $5 each. sh spent a total of $30.

Question

anonymous · Answer

$$5c = 30$$

anonymous · Answer

@jytete : let the unknown   count  of cd that can be buyed in 30$  be x
and cost of 1  cd is  5$
then 5 * x = 30
x= 6 
hope you got it

anonymous · Answer

as you were reading the question, pay attention to fixed factor and uncertainness.
marry bought SOME used cds, for $5 EACH, she spend a TOTAL OF $30.
as we can see, SOME is definitely a uncertain factor. so we pick a variable x to replace this "SOME". then the question becomes
marry bought x used cds for $5 each, she spend a total of $30
then we can have the equation, which is 
5 * x = 30