What is the average of the integers from 25-41

The average of 25 and 41 is (1/2)(25+41) = (1/2)(66) = 33 .

Similarly ...
--The average of 26 and 40 is 33.
-- The average of 27 and 39 is 33.
-- The average of 28 and 38 is 33.
-- The average of 29 and 37 is 33.
-- The average of 30 and 36 is 33.
-- The average of 31 and 35 is 33.
-- The average of 32 and 34 is 33.
-- That leaves only 33.

So the average of all of those 17 integers is 33 .

One unique triangle, because those angles add up to 180, and that's how many degrees there are in one triangle.