m = 236, n = 632 si p = 708
a + b = m
b + c = n
a + c = p
a + b + c = ?
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a + b + 2c = n+ p => m + 2c = n + p => c = (n + p - m) / 2
(n + p - m) / 2 = c
(p + m - n) / 2 = a
(m + n - p) / 2 = b
(n + p - m + p + m - n + m + n - p) / 2 = c + a + b
(n + p + m) / 2 = c + a + b
(236 + 632 + 708) / 2 = 788 = c + a + b
a + b + c = 788
