Within how many standard deviations of the mean do all of the values fall 11 14 10 8 12 13 12 18 9 12 16 15 11 9 10

The mean is 12 and std dev 2.8
The max is 18 and min is 8
One std dev would be:
If you add 2.8 + 12 = 14.8
If you subtract 12-2.8 = 9.2
Two std dev would be:
14.8 + 2.8 = 17.6
9.2-2.8 = 6.4
All of the data falls within 2 std deviations to the left and 3 std deviations to the right of the mean.

Okay so for every triangle has three angles that always add up to 180 degrees. and to tell the difference between whether they are secure, right or obtuse is that acute: has one angle that is less than 90 degrees. right triangle means there is at least one angle that is exactly 90 degrees. and an obtuse angle has an angle that is bigger than 180 degrees. i’ll do #13 as an example: 13. 40 and 50 so if every triangle has 180 degrees 40+50= 90 degrees then180-90= 90 degrees so the third angle is 90 degrees and because this triangle has a 90 degree angle it means it is a right triangle