What equation can be solved to find one of the missing side lengths of a triangle?

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?

Add: (6x^2-5x+3) + (3x^3+7x-8) a. 9x^2+12x-5 b. 9x^2+2x+11 c. 9x^2+2x-5 d. 9x^2-2x+5

Which of the following questions describes the equation g + (-4) = -5? a)what number, when added to negative four, is equal to negative five? b)what number, when added to negative five, is equal to negative four? c)what number, when subtracted from negative four, is equal to negative five? d)what number, when subtracted from negative five, is equal to negative four?