On a number line, a number, b, is located the same distance from 0 as another number, a, but in the opposite direction. The
number b varies directly with the number a. For example b = 23 when a = -23. Which equation represents this direct
variation between a and b?
bs-a
-b=-a
b-a=0
b(-a) = 0

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?