Hello friends how are you​

When using the linear combination metho e linear combination method to solve a system of linear equations, the four options are:

Show your workcan a right triangle have this sides? *how to prove it without using the pythagorean theorema*

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?