8.
a = 12, a - 8 = 12 - 8 = 4; a + 10 = 12 + 10 = 22
a = 20, a - 8 = 20 - 8 = 12; a + 10 = 20 + 10 = 30
a = 28, a - 8 = 28 - 8 = 20; a + 10 = 28 + 10 = 38
a = 43, a - 8 = 43 - 8 = 35; a + 10 = 43 + 10 = 53
Ответ: при a = 12: a - 8 = 4, a + 10 = 22; при a = 20: a - 8 = 12, a + 10 = 30; при a = 28: a - 8 = 20, a + 10 = 38; при a = 43: a - 8 = 35, a + 10 = 53.