Work out giving ur answer as a mixer number

Rewrite the following without an exponent. (5/8)-1

Kayla made observations about the sellin price of a new brand of coffee that sold in the three different sized bags she recorded those observations in the following table 6 is $2.10 8 is $2.80 and 16 is to $5.60 use the relationship to predict the cost of a 20oz bag of coffee.

Need showing work for this problem 56.25 ×25.80