Flipping two coins gives four possibilities: HH, HT, TH, TT
So P(TT)=1/4
So we'd expect a quarter of the trials to be two tails.

trials expected to be two tails.
The mean is the average, so add all the numbers and divide by 7 (7 terms).
-14 is the sum, divided by 7 = -2
The mean is -2.
The value of 7 is in the hundreds place