Ответ: 15) а. 28·2/21 - (14·17/21 + 11·8/21 ) = 26·2/21 - 25·25/21 = 28·2/21 - 26·4/21 = 590/21 - 550/21 =40/21 = 1·19/21
Б. 8·5/20 + (4·17/20 - 3·18/20) = 8·5/20 + 4·17/20 - 3·18/20 = 9·4/20 = 9·1/5
16) А. (9- 2·3/11) + (2 + 1·5/11) = = 7·3/11 + 3·5/11 = 10·8/11
Б. ( 4 + 1·5/16) - ( 3 - 2·9/16 ) = 5·5/16 - 1·9/16 = 85/16 - 25/16 = 60/16 = 3·3/4