№1.
1) 11/15 - 1 9/10 = 22/30 - 1 27/30 = -(1 27/30 - 22/30) = -1 5/30 = -1 1/6
2) -1 1/6 + 5/18 = - 1 3/18 + 5/18 = -21/18 + 5/18 = - 16/18 = - 8/9
3) -8/9 * 0,9 = -8/9 * 9/10 = -8/10 = -0,8
4) -0,8+0,1=-0,7
№2.
1) 7/15 - 1 1/12 = 28/60 - 1 5/60 = -(1 5/60 - 28/60) = - (65/60 - 28/60) = -37/60
2) -37/60 + 9/20 = -37/60 + 27/60 = -10/60 = -1/6
3) 0,2: (-1/6) = 2/10 : (-1/6) = 2/10 * (-6) =-1,2
4) 0,8+(-1,2)=-0,4