Elementary linear algebra with applications (classic version) chapter 1.3 problem 7e

What is a good tip to follow in the day you take the aspire test or psat

"what factors influence the absorption of sunlight at earth's surface? "

Case # 51173878 weighs 814 pounds; case # 51173981 weighs 803 pounds; case # 51174058 weighs 817 pounds; case 51174178 weighs 815 pounds; case # 51174248 weighs 817 pounds; case # 51174495 weighs 781 pounds; case # 51174577 weighs 828 pounds. what are the case #'s of the two cases that weigh the same amount?