John works two jobs. as a security guard he earns $8.50 per hour. as a landscaper he earns $14 per hour. one week john worked a total of 60 hours and earned $691.50. how many hours did he work at each job?

Last month, a 770 g box of cereal was sold at a grocery store for $3.10. however, this month, the cereal manufacturer launched the same cereal in a 640 g box, which is being sold at $2.50. what is the percent change in the unit price?