Ответ: [tex]28(a — 1) + 52(a + 6) = \\ = 28a — 28 + 52a + 312 = \\ = 80a + 284[/tex]при а=5.867[tex]80a + 284 = \\ = 80 \times 5.867 + 284 = \\ = 469.36 + 284 = \\ = 753.36[/tex]Ответ: 753.36