There is a bag with only red marbles and blue marbles. The probability of randomly choosing a red marble is .
There are 20 red marbles in the bag and each is equally likely to be chosen.
Work out how many marbles in total there must be.

The path traveled by a bottlenose dolphin as it jumps out of water is modeled by the equation y=-0.4+3x, where t is the height above water and x is the horizontal distance in feet. if a beam of light is shone upward at an angle modeled by the equation x+y=10, at what height from the waters surface will the beam of light hit the dolphin