2^2 = 4
just think 2 written out TWO times (hence the SECOND power).
the expression for mean in this case is

with d standing for expenditure in December. Now solve for d:

The student has to spend $45 to meet his goal.
Distribute 6x into (x - 2y):
= 6x^2 - 12xy
Hope this helps.
When you cut along the diagonal, a right triangle is formed where the hypotenuse is the diagonal and the legs are the length and width of the rectangle (10 and 15 in this case)
Now use the pythagorean theorem to solve
10^2+15^2=325=c^2
c= approx 18.02775=length of the diagonal
Blaaaa you die.
Honestly I have no idea