1) -2,04 : 1/25 = -2 1/25 : 1/25 = - 51/25 * 25/1 = -51
2) 3, 61 : (-19/40) = - 361/100 * 40/19 = -38/5 = -7 3/5
3) -51 - (-7 3/5) = -43 2/5
4) -43 2/5 : (-2 4/5) = 217/5 * 5/14 = 31/2
5) 0,6 : (-0,9) = -6/10 * 10/9 = -2/3
6) 31/2 + (-2/3) = 93/6 - 4/6 = 89/6 = 14 5/6