1) $$(8 - 17 - 19 + 21)x = -7x$$
2) $$(-9 + 12 + 41 - 17)y = 27y$$
3) $$(2.6 - 1)a + (-5.4 + 2)b = 1.6a - 3.4b$$
4) $$(-5.6 + 8.2)c + (4.8 - 9.1) = 2.6c - 4.3$$
5) $$(4.6 - 8.3)m + (8.3 - 6.4)n - 5.1 = -3.7m + 1.9n - 5.1$$
6) $$(-2/3 - 1/8)a + (5/6 - 7/12)b = (-16/24 - 3/24)a + (10/12 - 7/12)b = -19/24 a + 3/12 b = -19/24 a + 1/4 b$$