`b, |2/3 - 3/4| - 4/15 . \sqrt{25/16} + (-2/3)^{5} : (-2/3)^{3}`
`= |-1/12| - 4/15 . 5/4 + (-2/3)^{2}`
`= 1/12 - 1/3 + 4/9`
`= -1/4 + 4/9`
`= 7/36`
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`c, (2 3/4 : 6/5 + 6 1/4 : 6/5) - (-8 1/2) + 1,25 : (-0,5)`
`= (11/4 . 5/6 + 25/4 . 5/6) + 17/2 + 5/4 : {-1}/2`
`= [5/6 . (11/4 + 25/4)] + 17/2 - 5/2`
`= [5/6 . 9] + 17/2 - 5/2`
`= 15/2 + 17/2 - 5/2`
`= 30/2`
`= 15`