The cost C of mailing a letter first class in the United States is $0,45 for the first ounce. Each added ounce, or fraction of an ounce, o, costs an additional $0.20.
1. Write an equation to represent the total cost, C, to mail a first class letter that
weighs n ounces.
C=

C= 0.25 + 0.20n

Step-by-step explanation:

Let n be the number of ounces of the letters.

As per given,

Cost per ounce = $0.45

Additional cost per ounce = $0.20

So, the equation to represent the total cost, C, to mail a first class letter that  weighs n ounces will be

C= 0.45 + (n-1)(0.20)

⇒ C= 0.45 + 0.20n-0.20

⇒ C= 0.25 + 0.20n

Hence, the required equation is  C= 0.25 + 0.20n .

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