It will be just under 2 hrs i.e. 112 minutes and 30 seconds
basically i broke it up in hours so john achieves 1/5 of the work per hour and bob acheives 1/3. Combined effort = 8/15. So 8/15 x what = 15/15 where 15/15 is the complete building of the house. This is basically 15/8 and multiply by...