18/7 * (4/9 + 15/18) =
1)4/9+15/18=8/18+15/18=23/18 2)18/7×23/18=27/7=3 2/7
18/7×(4/9+15/18)=4/9+15/18сокращаем=4/9+5/9=8+15/18=18/7×23/18 сокращаем 18 =1/7×23=23/7