(2/5 + (-0,5)) + (-1 1/4) = - 1 7/20 = - 1,35
1) 2/5 + (-0,5) = 2/5 - 1/2 = 4/10 - 5/10 = -1/10
или 0,4 - 0,5 = -0,1 - если в десятичных дробях
2) -1/10 + (-1 1/4) = -1/10 - 1 1/4 = -2/20 - 1 5/20 = -1 7/20
или -0,1 - 1,25 = -1,35 - в десятичных дробях
(0,6 + 2/3) + (-2 1/15) = - 4/5 = - 0,8
1) 0,6 + 2/3 = 3/5 + 2/3 = 9/15 + 10/15 = 19/15 = 1 4/15
2) 1 4/15 + (-2 1/15) = 1 4/15 - 2 1/15 = - (2 1/15 - 1 4/15) = - (1 16/15 -1 4/15) = - 12/15 = - 4/5 = - 0,8