Find the greatest common factor of these three expressions. 70y3, 50y2, and 20y

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?

Me d is also an option but i couldn't get it in the picture

Y=21.95x+10 y=22.45x solve by substitution