Natalie is at an anusment park. the didgems cost 2 tickets and the rollarcoster cost 5 tickets. with 50 tickets she rode 13 times. how many times did she ride the dodgems and rollarcoster?

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?