Estimate: 42 x 58 im not good a estimating problems

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?

Match the one-to-one functions with their inverse functions.

Find the solution set for this equation: t^2+7t=0 separate the two values with a comma.