Company S produces two kinds of stereos: basic and deluxe. Of the stereos produced by Company

Company S produces two kinds of stereos: basic and deluxe. Of the stereos produced by Company S last month, 2/3 were basic and the rest were deluxe. If it takes 7/5 as many hours to produce a deluxe stereo as it does to produce a basic stereo, then the number of hours it took to produce the deluxe stereos last month was what fraction of the total number of hours it took to produce all the stereos?
A.7/17
B.14/31
C. 7/15
D.17/35
E.1/2

let the total number of steros be x therefore we get 2x/3 (basic) and x/3 deluxe steros
lets assume that it takes y hours to produce one basic stero, accordingly it takes 7y/5 hours to produce one deluxe stereo.

Combining both together we get the following

hours to produce 2x/3 basic stereos = 2xy/3
and hours to produce x/3 deluxe stereos = 7xy/15

total hours =17xy/15

therefore we get

(7xy/15)/(17xy/15)

which derives to 7/17