The cost of 3 gallons of milk is $6.75. What is the cost of 7 gallons of milk?

$15.75

Step-by-step explanation:

Let the cost of 7 gallons of milk be x

Since

3 gallons of milk = $6.75

7 gallons of milk = x

Cross multiply

7 x 6.75 = 3 x X

47.25 = 3x

Divide both sides by 3

47.25/3 = 3x/3

15.75 = x

x = $15.75

7 gallons of milk cost $15.75

65

step-by-step explanation:

since your problem is x^4 = 81, what you have to undeo is the "to the fourth power" part.

the inverse (opposite operation) of "to the fourth power" is "to the fourth root".

  (x^4) ^ ¼   = 81 ^ ¼  

  81 = 3^4     so (3 ^ 4) ^ ¼   =   3 ^ 1   = 3

by hand: (3 ^ 4) ^ ¼   =   3 ^ (4 x ¼) = 3 ^ 1   = 3   (when you take a power to a power, multiply the exponents.)

or, do it by calculator. one way of finding the fourth root is to use ^ (1/4)

step-by-step explanation: