Respuesta :

The key is to work from the middle.

c - (d - e) - f = c - d + e - f

b - (c - d + e - f) - g = b - c + d - e + f - g

a - (b - c + d - e + f - g) = a - b + c - d + e - f + g

Answer:
a - b + c - d + e - f + g

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