2 3/4:(1 1/2-2/5)+(3/4+5/6)

1.5-0.4=1.1 9/12+10/12=19/12 2.75/1.1=2.5 2.5+19/12=300/120+190/120=490/120=49/12   Выбираем лучшее решение!

[latex]2\frac{3}{4}:(1\frac{1}{2}-\frac{2}{5})+(\frac{3}{4}+\frac{5}{6})=4\frac{1}{12}[/latex]   [latex]1) 1\frac{1}{2}-\frac{2}{5}=1\frac{1}{10}[/latex]   [latex]2) \frac{3}{4}+\frac{5}{6}=\frac{19}{12}=1\frac{7}{12}[/latex]   [latex]3) 2\frac{3}{4}:1\frac{1}{10}=\frac{11}{4}*\frac{10}{1}=\frac{10}{4}=2\frac{1}{2}[/latex]    [latex]4) 2\frac{1}{2}+1\frac{7}{12}=3\frac{13}{12}=4\frac{1}{12}[/latex]