`a, (2/3 - 1) - [1/3 - (5/3 - 1)]`
`= 2/3 - 1 - (1/3 - 5/3 + 1)`
`=2/3 - 1 - 1/3 + 5/3 - 1`
`= (2/3 - 1/3 + 5/3) + (-1 - 1)`
`= 2 - 2`
`= 0`
`b, (1/3 + 1/6) . 1/11 - 1/2 : (1 - 1/12)`
`= (2/6 + 1/6) . 1/11 - 1/2 : (12/12 - 1/12)`
`= 1/2 . 1/11 - 1/2 : 11/12`
`= 1/2 . 1/11 - 1/2 . 12/11`
`= 1/2 . (1/11 - 12/11)`
`= 1/2 . (-1)`
`= -1/2`
`c, -((sqrt(25))^2)/13 - (sqrt(81))/17 + 12/13 + (-25/17)`
`= -25/13 - 9/17 + 12/13 - 25/17`
`= (-25/13 + 12/13) + (-9/17 - 25/17)`
`= -13/13 - 34/17`
`= -1 - 2`
`= -3`
`d, 2^4 + 8 . [(-2)^2 : 1/2]^0 - 1/(2^2) *4 + (-2)^2`
`= 16 + 8 * 1 - 1/4 * 4 + 4`
`=16 + 8 -1 + 4`
`= 27`
