Jennifer bought 4 packages of of tacks .there are 48 tacks in a package . she used 160 of of the tacks to put up posters. how many tacks does she have left? explain

When you have 25 numbers, and jake picks 3 random numbers and puts them back, what is the chance bob has of picking those 3 numbers when he picks 6 random numbers (without putting them back)? explain.

Aquadrilateral has exactly one pair of parallel sides. which name best describes the figure?

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.