For the set B = {5, 7), determine n(B).​

3r2

Step-by-step explanation:

13hrs

Step-by-step explanation:

Initial Temperature = 21°c

final temperature = -18°c

rate of decrease = 3°c/hr

for every hour the temperature decreases by 3°c.

What time does it take to get to 0c  = . 21(°c) / 3(°c/hr)  = . 7hr

what time does it take to get to -18c  = 18(°c) / 3(°c/hr)   = . 6hr

Total Time taken  = . 7hr + 6hr = 13hr

Alternative solution

Initial Temperature = 21°c

final temperature = -18°c

rate of decrease = 3°c/hr

(21 + 18)°c/ 3(°c/hr) . = . 13hr