At the mall, leona bought a t-shirt and a book for a total of $23. the book cost $12. how much did the t-shirt cost?

(a) what is the unknown information?

(b) let x represent the unknown information. write an addition problem that models the problem

(c) solve the equation.

(d) answer the question.

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?