A = 2
b = 0
2a + 2b = 4 → 4a + 4b = 8
(4a + 4b = 8) - (4a - 3b = 8) → 7b = 0
b = 0
so a = 2
When working with functions (of all types), the average rate of change is expressed using function notation:

For the interval from x=7 to x=8,
1. find f(7) and f(8):
2. use given formula:

Answer: the average rate of change for the interval from x=7 to x=8 is 4374.
The answer is 45 because if you add 30 and 60 which equals 90 then you do 90 divided by 2.
The equations are e = 18+12t and a = 45+9t
Adrian will be father along in the book after 4 days. She will be 15 pages ahead of Ethan
Ethan's page number at the beginning of the month = 18
Adrian's page number at the beginning of the month = 45
Pages read by Ethan each day = 12 pages
Pages read by Adrian each day = 9 pages
Let e represent the page of the book that Ethan is on at the end of t days into the month. Let a represent the page of the book that Adrian is on at the end of t days into the month.
Formulating the equation we get the following:
e = 18 + 12t
a = 45 + 9t
Finding the page number of both Ethan and Adrian after 4 days by substituting the values in the equations we get:
e = 18+12(4)
e = 66
a = 45 + 9(4)
a = 81
Learn more about linear equations:
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