I'm confused how is the sum of all 4 numbers gotten in this simple problem? More inside?

The original equation says (total number of chairs)/(number of people) = (average number of chairs built by each person). I'm a little confused as to where the 42 came from, but presuming it was given in the problem, it is "the number of chairs they would have each had to build if they all built the same number of chairs". Multiplying that number times the number of people will give you the total number of chairs built as 42 chairs/person * 4 person = 168 chairs. It's kind of a weird way to give the total number of chairs, because why would they give you an average instead of the total. It's not just you who thinks it's weird... oh well...