Which of these is not a way to think about finding -12-7

Aphoto of a painting measured 13 x 17 inches the scale of the photo to the original painting is 1 inch to 3 inches. what is the size of this painting

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?

What is the domain of the step function f(x)=[2x]-1?