STAY OUT OF MY HOUSE YOU KIDS, I AM MR NEBBERCRACKER

We must first determine the shape of a rectangular prisms _ a0 to find area of the prism

The number if marbles of different colors stored in a hat is listed below: 4 red marbles 10 green marbles 7 blue marbles. without looking in the hat, dan takes out a marble at random. he replaces the marble and then takes out another marble from the hat. what is the probability that dan takes out a blue marble in both draws?

[10 points, algebra 2-simplifying complex fractions]according to my answer key the restrictions are -1 and 4. but why not positive 1?