The museum of fine arts decides to expand its collection of European, Latin American and African art. After reviewing their current collection, the museum decides to purchase a total of 78 pieces. The curator wants 18 more pieces of African Art than Latin American Art. She wants 15 fewer pieces of European art than Latin American Art. how many of each

Ineed with number 6 , explain how to get 1978

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Set $r$ is a set of rectangles such that (1) only the grid points shown here are used as vertices, (2) all sides are vertical or horizontal and (3) no two rectangles in the set are congruent. if $r$ contains the maximum possible number of rectangles given these conditions, what fraction of the rectangles in set $r$ are squares? express your answer as a common fraction.