I need help with part b and c pretty p please show your work so I can do this

While scuba diving, rajeev dove to a depth of 12.6 feet below the surface of the water and then descended another 8.7 feet. what expression can be used to find rajeev's new position? 12.6 – 8.7 –12.6 – 8.7 –12.6 – (–8.7) 12.6 – (–8.7)

The standard deviation for a set of data is 5.5. the mean is 265. what is the margin of error?

8. kelly wants to buy a magazine that is $25. later the magazine was marked up an additional 20%. what is the new price?