Oblicz. a) 1 1/5 * 1 2/3

a)

`1 1/5*1 2/3*1/7+(1 1/7)^2=` `strike(6)^2/strike(5)^1 * strike(5)^1/strike(3)^1 * 1/7 + (8/7)^2`  = `2/1 * 1/7 + 64/49`   = `2/7 + 64/49`  = `14/49 + 64/49` = `78/49` = `1 29/49`

b)

`(2 1/6 - 2/3)^2 - 2 1/5`   = `(13/6 - 4/6)^2 - 11/5` = `81/36 - 11/5` = `405/180 - 396/180` = `9/180` = `1/20 ` 

c)

`10 - 2 * (3 1/5 - 2 1/4 * 1/3)`  = `10 - 2 * (16/5 - 3/4)` =`10 - 2 * ( 64/20 - 15/20)` =`10 - strike(2)^1 * 49/strike(20)^10`  = `10 - 49/10` = `10 - 4 9/10` = `5 1/10`  

d)

`( 7/3 - 5/12 + 1 1/2) : ( 2 3/4 - 5/6)` = `(28/12 - 5/12 + 1 6/12) : (2 9/12 - 10/12)` = `(28/12 - 5/12 + 18/12) : (33/12 - 10/12)` = `41/12 : 23/12` = `41/strike(12)^1 * strike(12)^1/23` = `41/23` = `1 18/23`