a cat and a mouse together weigh 10kg

a dog and a mouse together weigh 20kg

a dog and a cat together wiegh 24kg

HOW MANY KGS DO THEY ALL WEIGH TOGETHER?

Weight of cat and mouse = 10kg

so C + M = 10 kg (i)

similarly D + M = 20kg(ii)

and D + C = 24kg(iii)

adding (i) ,(ii) and (iii) we get

C + C + D + D + M + M = 10 + 20 + 24 = 54kg

so 2C+2D+2M = 54 kg

taking 2 as common

so 2(C+D+M) = 54kg

so  (C+D+M) = 54/2 = 27kg

so cat,mouse and dog together weigh 27 kg.