SOLUTION: Rita has three pets: Jen the rabbit, Joe the dog, and Jill the cat. Rita has a problem measuring the weight of each animal because whenever she places one animal, at least one othe

Let R be the rabbit's weight;

    D be the dog's    weight;

    C be the cat's    weight.


From the condition, you have these tree equations


    R + C = 10        (1)

    R + D = 20        (2)

    C + D = 24        (3)


To solve the system, add all three equations.  You will get


    2R + 2C + 2D = 10 + 20 + 24 = 54


or, dividing both sides by 2


    R + C + D = 27.    (4)


Now,  from equation (4) subtract equation (1).     You will get  D = 27 - 10 = 17 kg(weight of the dog).


Next, from equation (4) subtract equation (2).     You will get  C = 27 - 20 =  7 kg(weight of the cat).


Finally, from equation (4) subtract equation (3).  You will get  R = 27 - 24 =  3 kg(weight of the rabbit).