5) - 5/9 + 5/6 = - 10/18 + 15/18 = 15/18 - 10/18 = 5/18
6) - 1 1/8 - 2 5/16 = - (1 1/8 + 2 5/16) = - (1 2/16 + 2 5/16) = - 3 7/16
7) (3.9 - 5.8) - (- 1/45 - 7/9) + 1.1 = (-1.9)-(-(2/90+70/90))+1.1 = (-1.9)-(-72/90)+1.1 = (-1.9)-(-0.8)+1.1 = - 1.9+0.8+1.1 = 0
9) х + 2 2/21 = - 3 5/14
Х = - 3 5/14 - 2 2/21
Х = - (3 15/42 + 2 4/42)
Х = - 5 19/42