The cost to mail a one ounce letter was 39 cents and the cost to mail a two once letter was 63 cents. what is the ratio of the cost to mail a one ounce letter to the cost to mail a two ounce letter

Cherie works in retail and her weekly salary includes commission for the amount she sells. the equation s=400+0.15c models the relation between her weekly salary, s, in dollars and the amount of her sales, c, in dollars. interpret the slope of the equation.