Jake is comparing the cost of a fresh lobster dinner at two different restaurants. The first
restaurant charges $42 for the meal, plus $3 per kilogram for the lobster he picks. At the
second restaurant, Jake would pay $6 per kilogram for the lobster, in addition to $39 for the
meal. Jake realizes that, in theory, dinner at both restaurants could cost the same amount if
the lobster had a certain weight. What is the weight? How much would Jake pay for his
dinner?