`-3/4 + 1/6 + (-7)/8`
`= -18/24 + 4/24 + (-21)/24`
`= (4 - 18 - 21)/24 = -35/24`
`-2/3 + (-1)/3 ÷ 0,2 + 25%`
`= -2/3 - 1/3 ÷ 1/5 + 1/4`
`= -2/3 - 5/3 + 1/4`
`= (-2 - 5)/3 + 1/4`
`= -7/3 + 1/4`
`= 3/12 - 28/12 = -25/12`
`-3/4 . 7/8 + 1 1/2 + (-3)/4 ÷ 8/9`
`= -3/4 . 7/8 + 3/2 + (-3)/4 . 9/8`
`= -3/4 (7/8 + 9/8) + 3/2`
`= -3/4 . 2 + 3/2`
`= -3/2 + 3/2 = 0`