He swam 1,800 laps total in 12 weeks. Each week, he swam 150 laps because 1800/2=150 in 5 days. Each day, he swam 30 laps because 150/5=30, in 45 minutes. His average time was 30/45=2/3 At that rate, in one hour, he would swim 2/3*60 = 2/3 x 60 = 40 laps/hour Final answer is 40