Since there are 60 minutes in an hour, then Mr. Willson worked for 60 minutes x 3/4 = <<60*3/4=45>>45 minutes on Monday.
He worked for 60 minutes/2 = <<60/2=30>>30 minutes on Tuesday.
He worked for 60 minutes x 2/3 = <<60*2/3=40>>40 minutes on Wednesday.
He worked for 60 minutes x 5/6 = <<60*5/6=50>>50 minutes on Thursday.
So Mr. Willson worked for 45 + 30 + 40 + 50 + 75 = <<240=240>>240 minutes.
In hours, it is equal to 240/60 = <<240/60=4>>4 hours.
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