A group of students stand at a table during lunch asking others to participate in a survey. What type of sample or survey is this? A. controlled experiment B. convenience C. systematic sample ​

Which is an equation for the nth terms of the sequence 12,15,18,21

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?

3/4 + p = 1/2? i’m not sure how to solve it