Sorry if this isn't clear It's a ratio question. Henry does 3 hrs for every one of Samuel's 2hrs, the ratio is 3:2 The total number of parts is 5 and to work out one part, divide 20 by 5 =4 So if Henry does 3hrs for Sam's 2hrs, he does 4 x 3 to get his part of the total 20hrs 4 x 3 = 12 And Sam does 2hrs, he does 4 x 2 = 8 So Henry does 12hrs a month