Need on this two column proof for geometry

An ulcer medication has 300 milligrams in 2 tablets. how many milligrams are in 3 tablets?

Solve for x and select the correct answer

Answer asap and if you do you will get brainliest. catherine buys a gallon of ice cream from the store. after taking it home, she eats a fifth of a gallon of ice cream. her sister eats some of the ice cream as well. if two-thirds of the original amount of ice cream is left, then what fraction of a gallon of ice cream did her sister eat?