21+6а+28-2а=-19
4а=-19-21-28
4а=-68
а=-17
3*(7 + 2а) - 4*(-7 + 0,5а) = -19,
21 + 6а + 28 - 2а = -19,
6а - 2а = -19 - 21 - 28,
4а = -68,
а = -17
21+6а+28-2а=-19
4а=-19-21-28
4а=-68
а=-17
3*(7 + 2а) - 4*(-7 + 0,5а) = -19,
21 + 6а + 28 - 2а = -19,
6а - 2а = -19 - 21 - 28,
4а = -68,
а = -17