Help please

Question

A web music store offers two versions of a popular song. The size of the standard version is 2.5 megabytes (MB). The size of the high-quality version is 4.9 MB. Yesterday, there were 710 downloads of the song, for a total download size of 2279 MB. How many downloads of the high-quality version were these?

Answer 1

let s=#std downloads and h=#high quality downloads

 

s+h=710

2.5s+4.9h=2279

 

Solve the linear system

(multiply first equation by -2.5 and add equations)

 

2.4h=2279-2.5*710 

h=210, plugging back into 1st equation gives us

s=500