## Boy, girl and dog

Let's consider:

a = boy's weight

b = weight of the girl

c = dog weight

For the three weighings shown in the figure, we have:

a + b = 118

b + c = 72

a + c = 78

Summing the three equations, we have:

2a + 2b + 2c = 268

Simply put, we have:

a + b + c = 134

Therefore, the three together weigh 134 kg.

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