1.
17 ≤ х ≤ 41,
х = 17, 18, 19, ...., 40, 41,
из которых 17, 19, 23, 29, 31, 37, 41 - простые числа,
∑(17⇒41) = 17 + 19 + 23 + 29 + 31 + 37 + 41 = 197 (С),
2.
80 = 2*40,
120 = 3*40 НОД (80, 120) = 40,
40 = х+4х,
40=5х,
х=8 - меньшее,
4х=32 - большее (Д),
3.
НОД (48, а) = 24,
НОК (48, а) = 144,
144 : 48 = 3,
48 : 24 = 2 ⇒ а = 24 * 3 = 72 (Д),
4.
42/48 = (2х-1)/8,
48*(2х-1) = 42*8,
96х - 48 = 336,
96х = 336 + 48,
96х = 384,
х = 4 (В)