3 3/14 : ( 1 3/7-5/21•0,9)-0,79

3 3/14 : (1 3/7 - 5/21 * 0,9) -0,79=1 1457/17005/21*0,9=5/21*9/10= 3/141 3/7 - 3/14 = 1 3/143  3/14 : 1 3/14 = 2 11/172 11/17-0,79 = 2 11/17 - 79 /100 = 1 1457 /1700