Let the cat is represented by C, dog by D and rabbit by R, then
C+D=24......(1)
C+R=10......(2)
D+R=20.......(3)
(1)-(2)implies
D-R=14.......(4)
(3)+(4)
Implies
2D=34
So, D=34/2 = 17Kg
Therefore from (1)
C=24-D=24-17=7Kg
From (2)
C+R=10
R=10-C=10-7=3Kg
Therefore the weight of dog, cat and rabbit are 17, 7 and 3 respectively