237. A part-time employee whose hourly wage was increased by 25 percent decide to reduce the number of hours worked per week so that the employee's total weekly income would remain unchanged. By what percent should the number of hours worked be reduced? 12.5% 20% 25% 50% 75% Key is 20% 不会列方程，找不出足够的等量。也找不出该设哪个为未知数？ | 
