If a system of equations does not have the variables all lined up, how could you still use elimination? Explain.

Which of the following statement about pascal's triangle are true?

Which letters from the table represent like terms? a and b b and c a and d b and d

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.