21.25% because 85/400 = .2125 which is 21.25%
Your sequence
-8, 16/3, -32/9, 64/27
is a geometric sequence with first term -8 and common ratio
(16/3)/(-8) = (-32/9)/(16/3) = -2/3
The general term an of a geometric sequence with first term a1 and ratio r is given by
an = a1·r^(n-1)
For your sequence, this is
an = -8·(-2/3)^(n-1)
The answer is 15
Since 20 times 7 is 140 and 140+75 is 215
Take 215-200 you get 15
3 in the power of ten means "10^3."

How to solve exponents is to multiply the number as many times as it's exponent. So in this case you will have to multiply ten, three times.

Which would mean that....

The answer is 10^3.
Hope this helps.