Please help I don’t know what the answer is

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?

Define the type of sequence below. 7, 14, 28, 56, 112, a. neither arithmetic nor geometric b. arithmetic c. both arithmetic and geometric d. geometric

What 8/12+8/11 in another way than and improper fraction