This week, Emmett's family watched 15.6 hours of TV. That is 60.4% more hours than they watched last week. How many hours of TV did Emmett's family watch then? Round your answer to the nearest tenth.
Let E be the number of hours Emmett's family watched last week.
The number of hours they watched this week is E + E * 60.4% = E + 0.604E = 1.604E = 15.6 hours.
Thus, they watched E = 15.6 hours / 1.604 = <<15.6/1.604=9.719>>9.7 hours of TV last week. Answer: \boxed{9.7}.