15 oxen take 80 days so, 6 oxen take \(x\) days
\(x=15^{*} 80 / 6=200\) days
20 oxen also take 80 day. So, 2 cows take y days
\(y=20^{*} 80 / 2=800\) days
Together work will be done in \(800 \star 200 /(800+200)=160\) days