If DE = 4x+10 and EF= 2x-1 and DF = 9x-15 find DF

Which equation results from adding the equations in this system? x+6y=9 and -x+2y=-15

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?

Arectangle has a perimeter of 24 inches. if the width is 5 more than twice the length, what are the dimensions of the rectangle?