Problem 2. One dog, one cat, and one rabbit have a mass of 17 kg, two dogs, one cat, and one rabbit 29 kg, and two dogs, three cats, and one rabbit 35 kg. What are the masses of one dog, one cat, and one rabbit?
Solution. In the second sum of weights, we have one more dog than in the first sum, so the difference in weight between the second sum and the first sum will give us the weight of one dog, i.e., $29-17=12$ kg. In the third sum, we have 2 more cats than in the second sum, so the weight of two cats will be the difference $35-29=6$ kg, from which the weight of one cat is 3 kg. From the first equation, we have that the weight of one rabbit is $17-(12+3)=2$ kg.