[Deaf Smith]

Why?

[NWFree]

My dog chases rabbits

[Craftmore]

nothing,the rabbit runs one direction,the cat another,and the dog goes nuts

[Some Fat Guy in L.A.]

A rabbit bit my sister once.

[Alberta's Child]

27 kg.

[linMcHlp]

2 x (cat + rabbit) = (dog + rabbit)

dog = (24 - cat)

[Secret Agent Man]

27kg

[StormEye]

Dog + Cat + Rabbit =27kg.

[Gene Eric]

I think this is correct:

rabbit = 20g - dog
cat = 10g - rabbit
dog = 24g - cat

rabbit = 20g - (24g - cat)
rabbit = 20g - 24g + cat
rabbit = 20g - 24g + 10g - rabbit
2 rabbits = 6g
rabbit = 3g

dog + cat = 24kg
dog + cat + rabbit = 27g

cat = 7g
dog = 17g

[Repeal The 17th]

That is not algebra.

[DouglasKC]

Never happen unless they’re dead. Too much chaos otherwise.

[Dr. Sivana]

59.52481 pounds. I used no algebra.

[EastTexasTraveler]

29
Cat = 5
Rabbit = 5
Dog = 19

[bunkerhill7]

A dog and a cat weigh the same as a dog , a cat and a hair.

[sasquatch]

Tastes like chicken.

[SpaceBar]

The ‘standard’ way is to substitute into one equation from the others, eliminating all but one variable, then substituting that known back into the others, thus solving the simultaneous system, and thus the sum once all unknowns are known. A more elegant approach when the number of variables gets hard to handle like a million or so is inversion of the matrix of coefficients operating on the RHS of the system yielding the unknowns in one fell swoop. And yes D=17, C=7, R=3, and thus Σ=27.

[ProtectOurFreedom]

I remember around fifth or sixth grade we would have puzzles like that and we would have to solve them by inspection because we didn't know symbolic algebra. Those problem drove me crazy. I suppose the really smart kids developed their own algebra to solve them.

I started learning symbolic notation in 8th grade, then, in ninth grade came Algebra 1 with simultaneous equations. Suddenly, things got SO much easier.

You posed a simple set of three simultaneous equations with three variables. Solve by successive substitution.

I went on to become a mechanical engineer. I might even remember how to ride a bike, too.

[leopud]

C + R = 10
d + R = 20
d + c = 24
C+d+R=x
10 – c = 20 – d
d – c = 10
d+c=24
d = 10 + c
d = 24 – c
10+c = 24-c
2c=14
c=7
d=17
R=3
C+d+R=27

[Sgt_Schultze]

[The people have spoken]

Use Wolfram’s Mathematica:

Solve[{c + r == 10, d + r == 20, d + c == 24}, {c, d, r}]

Output is {{c -> 7, d -> 17, r -> 3}}

Answer is 7+17+3 = 27