Упростите выражение: 1) $$-4,2x \cdot (-6y);$$ 2) $$8m + 5p - 13m - p;$$ 3) $$k-(17-k) + (-k+30);$$ 4) $$-6(4 + a) + 8(a - 6).$$

1) $$-4,2x \cdot (-6y)$$ = $$25.2xy$$ 2) $$8m + 5p - 13m - p = (8m - 13m) + (5p - p) = -5m + 4p$$ 3) $$k-(17-k) + (-k+30) = k - 17 + k - k + 30 = k + 13$$ 4) $$-6(4 + a) + 8(a - 6) = -24 - 6a + 8a - 48 = 2a - 72$$