Answer:
72 minutes or 1 hour and 12 minutes
Step-by-step explanation:
in one hour Raymond would have done 1/3 of a job
in one hour Robert would have done 1/2 of a job
so in one hour together, they would have done 1/2+1/3 = 5/6 of a job
5/6 job = 1 hr
1/6 job = 12 mins
6/6 job = 72 minutes
