@LafonateBVB Schmutz. Schlotterbeck will Titel gewinnen, vielleicht sollte er mal lernen die Beine geschlossen zu halten. Dieser Verein ist nicht mehr zu retten
This is simple.
Let Cat = C
Rat = R
Dog = D
C + R = 10, that is R = 10 - C.
D + R = 20, that is D + 10 - C = 20. This means that D - C = 10, and D = C + 10.
Then, C + D = 24, that is C + C + 10 = 24. This means 2C = 14. That is C = 7.
Substituting into our earlier equations, can then get R = 3 and D = 17.
Finally, C + D + R =?
That is 7 + 17 + 3 = 27.