If you add Natalie's age and Fred's age, the result is 45. If you add Fred's age to 4 times Natalie's age, the result is 87. Write and solve a system of equations to find how old Fred and Natalie are.

The radius of the earth is two times the radius of the moon. what fraction of the volume of the earth is the volume of the moon?

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.

[tex]5 \times1 \frac{12}{13} [/tex] me