Roberta is thinking about joining the food co-op store. if she pays $10.00 to join, she will get 10% off on all the groceries she buys there. how much must she buy before her savings equal her membership fee?

Really need on these. i have no idea what to do

Afamily has five members. a mom, a dad, two sisters, & a brother. the family lines up single file. what is the probabillity that the mom is at the front of the line

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.