Вычислите.
(5/8-2/5)+3/20=
1/5+(5/9-1/4)=
5/6-(3/10+2/5)=

( 5/8 - 2/5 ) + 3/20 = ( 25/40 - 16/40 ) + 3/20 = 9/40 + 3/20 = 9/40 + 6/40 = 15/401/5 + ( 5/9 - 1/4 ) = 1/5 + ( 20/36 - 9/36 ) = 1/5 + 11/36 = 36/180 + 55/186 = 91/1805/6 - ( 3/10 + 2/5 ) = 5/6 - ( 3/10 + 4/10 ) = 5/6 - 7/10 = 50/60 - 42/60 = 8/60 = 2/15