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 .

7x^2-4x+3y^2      ( the ^ means the exponent EX: 5^2 is 5 squared. )

Step-by-step explanation:

Remove the parenthesis (a) = a

12x^2-11y^2-13x- (5x^2-14y^2-9x)

-(5x^2 - 14y^2 - 9x)

Distribute parenthesis

-(5x^2) - (14y^2) - (-9x)

Apply minus - plus rules

-5x^2 + 14y^2 + 9x

= 12x^2 - 11y^2 - 13x - 5x^2 + 14y^2 + 9x

Simplify

12x^2-11y^2-13x-5x^2+14y^2+9x

Group like terms

12x^2-5x^2-13x+9x-11y^2+14y^2

Add similar elements

7x^2-13x+9x-11y^2+14y^2

Add similar elements ( - 13x + 9x = -4x )

7x^2-4x-11y^2+14y^2

Add similar elements 11y^2 + 14y^2 = 3y^2

7x^2-4x+3y^2