Hi please help me I need to find the value of x and I'm unsure how to do so do please solve this and walk me through it step by step (3x)/2+7/4=5-3/7

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?