`1)`

`a) (-2)/19 + 8/13 - 17/19+ 1 3/4 + (-5)/(-13)`

` = ((-2)/19 - 17/19) + (8/13 + 5/13) + 1 3/4`

` = -1 + 1 + 1 3/4`

` = 0 + 1 3/4`

` = 1 3/4 = 7/4`

`b) 9/7 - 2/7 : 0,25 + 2/3`

` = 9/7 - 8/7 + 2/3`

` = 1/7 + 2/3`

` = 3/21 + 14/21`

` = 17/21`

`2)`

`a) 1/8 + x = 0,5 . 3/4`

`1/8 + x = 3/8`

`x = 3/8 - 1/8`

`x = 2/8 = 1/4`

`b) 1/2x+2/3x-1=3 1/3`

`x.(1/2+2/3)=3 1/3 + 1`

`x . 7/6 = 13/3`

`x = 13/3 : 7/6`

`x = 26/7`