2/5 м - 1/10 м = 4/10 - 1/10 = 3/10 - сторона DE
19/20 - ( 2/5 + 3/10 ) = 19/20 - ( 4/10 + 3/10) = 19/20 - 7/10 = 19/20 - 14/20 = 5/20 = 1/4 - CE
2/5 м - 1/10 м = 4/10 - 1/10 = 3/10 - сторона DE
19/20 - ( 2/5 + 3/10 ) = 19/20 - ( 4/10 + 3/10) = 19/20 - 7/10 = 19/20 - 14/20 = 5/20 = 1/4 - CE