Помогите решить:(3/14+5/21у):3/7=З 1/4

(3/14+5/21y):3/7=3 1/4 1/98+5/441y=13/4 y=1143/4 y=285.75

[latex](\frac{3}{14}+\frac{5}{21}y):\frac{3}{7}=3 \frac{1}{4}[/latex] [latex]3\frac{1}{4}=\frac{3*4+1}{4}=\frac{13}{4}[/latex] [latex]\frac{3}{14}+\frac{5}{21}y=\frac{13*3}{4*7}[/latex] [latex]\frac{3}{14}+\frac{5}{21}y=\frac{39}{28}[/latex] домножим на 7*3*2*2, получим [latex]3*6+4*5y=39*3[/latex] [latex]18+20y=117[/latex] [latex]20y=118-18[/latex] [latex]20y=99[/latex] [latex]y=\frac{99}{20}[/latex] ------------------------------------------------------- [latex](\frac{3}{14}+\frac{5}{21}y):\frac{3}{7}=3 \frac{1}{4}[/latex] [latex](\frac{3}{14}+\frac{5}{21}y)*\frac{7}{3}=\frac{13}{4}[/latex] [latex]\frac{1}{2}+\frac{5}{9}y=\frac{13}{4}[/latex] [latex]\frac{5}{9}y=\frac{13}{4}-\frac{1}{2}[/latex] [latex]\frac{5}{9}y=\frac{11}{4}[/latex] [latex]y=\frac{11*9}{4*5}=\frac{99}{20}[/latex]