`PIET!?A`

`A = (0,75 - 0,6 + 3/7 + 3/13) : (11/7 + 11/13 + 2,75 - 2,2)`

`= (3/4 - 3/5 + 3/7 + 3/13) : (11/7 + 11/13 + 11/4 - 11/5)`

`= 3(1/4 - 1/5 + 1/7 + 1/13) : 11(1/7 + 1/13 + 1/4 - 1/5)`

`= 3/11`.

`B = ((10\sqrt{1,21})/7 + (22\sqrt{0,25})/3) : (5/\sqrt{49} + \sqrt{225}/9)`

`= ((10 * 1,1) / 7 + (22 * 0,5) / 3) : (5/7 + 15/9)`

`= (11/7 + 11/3) : (5/7 + 5/3)`

`= 11(1/7 + 1/3) : 5(1/7 + 1/3)`

`= 11/5`.

`C = \sqrt{4/8} : \sqrt{25/81} - 1 2/5`

`= \sqrt{1/2} : 5/9 - 7/5`

`= (1/\sqrt{2}) * (9/5) - 7/5`

`= 9/(5\sqrt{2}) - 7/5`

`= (9\sqrt{2})/10 - 14/10`

`= (9\sqrt{2} - 14)/10`.