дам 20 балов -2/5-(-3/5) ; -3/7-(+4/7) ; 1/9-(+2/9)

-2/5-(-3/5)=-2/5+3/5=1/5=0,2-3/7-(+4/7) =-3/7-4/7=-7/7=-11/9-(+2/9)=1/9-2/9=-1/9

- 2/5 - ( - 3/5 ) = - 2/5 + 3/5 = 1/5 = 0,2 ; - 3/7 - ( + 4/7 ) = - 3/7 - 4/7 = - 3 - 4 / 7 = -7/7 = -1 ; 1/9 - ( + 2/9 ) = 1 - 2 / 9 = - 1/9