The expression of the height is

the index "n" is the numbers of times that the ball is down, to n=1 the height is 8 inches, to n=2 the height is 4 inches.
An when n=5, the height is

the anwers is 0.5 inches
let h= history books
science books = s
h=2s there are 2 times as many history as science so to get them equal we double the science
h+s=81 there are 81 total history and science books
2s+s=81 substitute 2s for h in the above equation
3s = 81 combine like terms
s = 27
There are 27 science books
h=2s
h=2(27)
h=54
there are 54 history books
Answer:
102
Step-by-step explanation:
89 + a
Let a=13
89+13
102
I think the group 2 survey is likely to be biased towards people who are not too keen on zoos since all the values are small.
From group 1 and 3 the mean number of visits are
(4 + 10 + 6 + 3 + 8 + 7 + 9 + 3 + 4 + 7) / 10
= 61/10
mean = 6