Answer:
Shipping Fee = $ 6
Step-by-step explanation:
The complete question and the table is as follows :
Given - Julio is ordering books from Best Books for his reading club. The table shows Julio's total cost of the book order, Including the shipping fee for each order. Best Books charges the same shipping fee for every book order.
To find - How much is the shipping fee?
Proof -
We know that,
Total Cost = (Number of books buy)(Cost of 1 book) + Shipping Fee
Let us Assume that,
Cost of 1 book = x
Shipping Fee = y
So,
From the table, we get
21 = 5x + y ..........(1)
36 = 10x + y ..........(2)
51 = 15x + y ..........(3)
66 = 20x + y ..........(4)
From equation (1), we get
y = 21 - 5x
Put the value of y in equation (2), we get
36 = 10x + 21 - 5x
⇒36 = 5x + 21
⇒5x = 36 - 21
⇒5x = 15
⇒x = = 3
∴ we get
x = 3
Put the value of x , we get
y = 21 - 5(3)
= 21 - 15
= 6
⇒y = 6
SO, we get
x = 3
y = 6
Verify the 4 Equations :
21 = 5x + y ..........(1)
21 = 5(3) + 6
= 15 + 6
= 21
⇒21 = 21
Verified
36 = 10x + y ..........(2)
36 = 10(3) + 6
= 30 + 6
= 36
⇒36 = 36
Verified
51 = 15x + y ..........(3)
51 = 15(3) + 6
= 45 + 6
= 51
⇒51 = 51
Verified
66 = 20x + y ..........(4)
66 = 20(3) + 6
= 60 + 6
= 66
⇒66 = 66
Verified
So, we get
Cost of 1 book = x = $ 3
Shipping Fee = y = $ 6
