weight ratio Santi,Annisaa, and Rina is 7:6:8,if weight Rina 12 kg heavier than the annisaa, then the amount weight loss is the third child .............

Annisa : Rina = 6 : 8
Rina = 12 + Anissa
hence
8x = 12 + 6x
2x = 12
x = 6.
We got constant factor of 6. Therefore, multiply it to the comparison of the weight.
Santi's weight = 7 × 6 = 42
Annisa's weight = 6 × 6 = 36
Rina's weight = 8 × 6 = 48.
The total amount of the weight is 42 + 36 + 48 = 126 kg