Aweb music store offers two versions of a popular song. the size of the standard version is 2.2 megabytes (mb). the size of the high-quality version is 4.6 mb. yesterday, there were 1190 downloads of the song, for a total download size of 3386 mb. how many downloads of the standard version were there?

Standard version is  s
high quality  version is h
2.2s - how many MB takes standard version
4.6h - how many MB takes high quality  version 

we got system of equations
s+h=1190
2.2s +4.6h =3386

h=1190-s  substitute it into second equation
2.2s +4.6(1190-s) =3386
2.2s+4.6*1190 - 4.6s =3386
- 2.4s= 3386-4.6*1190
- 2.4s= 3386-5474
- 2.4s= -2088
s = 870