Question 628692
The Internet Book Company charges $6 postage for 2 books, and $10 postage for 5 books.
a) Find an equation relating the postage charge and number of books.
b) How much will it charge to post 8 books?

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Let x be the number of books and y be the cost of books

a.Find an equation relating the postage charge and number of books.

We have two points (2, 6) and (5, 10)

The slope is:

m = (10 - 6)/(5 - 2) = 4/3

The equation will be:

y - 6 = 4/3(x - 2)

y - 6 = 4x/3 - 8/3
y = 4x/3 + 6 - 8/3
y = 4x/3 + 10/3

b.How much will it charge to post 8 books?

We know the equation

y = 4x/3 + 10/3 

If x = 8 then
y = 4(8)/3 + 10/3 = 32/3 + 10/3 = $14

So it will charges $14 for 8 books.

John10