\(1hr=60mins\)
\(60x3mins\)
Basically meaning in 20 hours time but then we need include the full hour.
\(60x20=1200mins\)
\(3x20=60mins\)
\(1200+60=1260\)
Conversion: \(\frac{1260}{60} =21hr\)
\(6pm\) on saturday + \(21hr=3pm\) on sunday
Hope this helps