**Explanation : **
Let the duck be ‘Du’
The dog be ‘Do’
The rabbit be ‘R’.
From the above picture,
we can form equations as,
R + Du = 10kg.…equation (1)
R + Do = 20kg….equation (2)
Do + Du = 24kg…equation (3)
& R + Do + Du = ?
Rearranging the equations,
equation (1) = R + Du = 10kg
Du = 10kg – R
equation (2) = R + Do = 20kg
Do = 20kg – R
Putting the values of Do & Du in equation (3),
Do + Du = 24kg
20kg – R + 10kg – R = 24kg
30kg – 2R = 24kg
2R = 6
Rabbit, R = 3kg
Substituting the value of R, in equation (1) & equation (2)
We get,
equation (1), R + Du = 10kg
3 + Du = 10kg
Duck, Du = 7kg
Also, equation(2), R + Do = 20kg
3 + Do = 20kg
Dog, Do = 17kg.
Adding the values of,
Do + Du + R = 3 + 7 + 17
Dog + Duck + Rabbit = 27kg.