Change of base is

change base to 3

why would you want base 3? base 10 is on most calculators
anyway, the value would be 2.809555
The mean is the average of a set of numbers. You add all of your numbers together (example = 1+5+3= 9), then you divide the answer by the number of numbers you have used ( 9 divided by 3 = 3) so the mean is 3
a triangle needs to have 180 degrees in all.
65 + 65 = 130
180 - 130 = 50
x = 50 degrees
-8-3=-5. there . thats the answer.