It is a they need 27 canoes.
Let the number be a ....
=>Number doubled : 2a ..
=>Eight less than the no. Doubled : 2a - 8
=>Eight less than the no. doubled is 20 more than the no. : 2a - 8 = 20 + a
=>2a - 8 - 20 - a = 0
=>2a -a - 20 -8 = 0
=>a -28 = 0
=>a = 28
=>so the number is 28...
Hope it helps!!!
The expected duration of the activity is 29 days and 4 hours.
Step-by-step explanation:
Step 1:
The optimistic time,
= 25 days,
The most likely estimate,
= 29 days.
The pessimistic time,
= 34 days.
According to PERT, the expected duration of the activity, 
Step 2:
By substituting the given values, we get
0.1666 days = 
29.1666 days approximately equal 29 days and 4 hours.