P = AB + BC + AC = 999
AB = BC + 76
AC = (AB + BC) : 2
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2 x AC = AB + BC
2 x AC = BC + 76 + BC
2 x AC = 2 x BC + 76 / : 2
AC = BC + 38
BC + 76 + BC + BC + 38 = 999
3 x BC+ 114 = 999 / - 114
3 x BC = 885
BC = 885 : 3 => BC = 295
AB = 295 + 76 => AB = 371
AC = 295 + 38 => AC = 333
V: 333 + 371 + 295 = 999