2,4(3х+2)+0,3(х+4)=6,6
7,2х+4,8+0,3х+1,2=6,6
7,2х+0,3х=6,6-1,2-4,8
7,5х=0,6
х=0,6/7,5
х=0,08
13/15 + 2 5/9 = 2 + (13/15+ 5/9) = 2 + (39/45+25/45) = 2 + 64/45=
= 2 + 1 19/45 = 3 19/45
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8 - 2 5/6 = 8 - 2 - 5/6 = 6 - 5/6 = 5 + 1- 5/6 = 5 + 6/6 - 5/6 = 5 1/6