At a particular music store, cds are on sale at $12.00 for the first one purchased and $9.00 for each additional disc purchased. maria spends $84.00 on cds. how many cds has maria purchased?

Maria purchased 9 CDs

Step-by-step explanation:

Maria spends $84.00 on CDs. The first CD is $12,  the rest $9

As the CD have different price ,  first we have to discount the price of the first one,  and then we divide the rest by $9

Price First CD = $12 ,

We buy the first ,  so we get the rest of money  84-12=72

Price Rest =$9 ,  with the money that left ,  we can buy 72/9= 8

Total= 1 +8 =9

not only in mathematics, scientific proof also are required in the other field of science. also maths proofs are of particular structure, containing steps and logics. so proving is like doing science, it is science. that's why it is important to prove. 

an inaccurate proof leads to errors, or stating results that are not accurate.  which wil mess the probelm up you dont want this