A negative plus a negative is a positive true or false

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?

The area of square garden is 300m squared. how long is the diagonal?

How can constraints be used to model a real-world situation?