Respuesta :

He is 38 kg.


I'll use only the first letters of their names, to make it simpler:

S+L=54.75
S+M=105
M=4L

S+4L=105
105-54.75=4L-L=3L
L=50.25/3=16.75
S=54.75-16.75=38

Answer:

38 kg

above is the answer

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