Louis is playing a video game. He begins with an initial score of 300 points but loses 120 points throughout the game. He represents his score using the expression shown. 300 – 120 Write the expression as an addition expression.

Assume that there is a 11% rate of disk drive failure in a year. a. if all your computer data is stored on a hard disk drive with a copy stored on a second hard disk drive, what is the probability that during a year, you can avoid catastrophe with at least one working drive? b. if copies of all your computer data are stored on four independent hard disk drives, what is the probability that during a year, you can avoid catastrophe with at least one working drive?