Question

2/7 : (5/7+11/21) помогите​

Answer 1

Решение и ответ:

$\displaystyle \frac{2}{7}\div\left({\frac{5}{7}+\frac{{11}}{{21}}}\right)=\frac{3}{{13}}$

$\displaystyle 1)\;\;\frac{5}{7}+\frac{{11}}{{21}}=\frac{{3\cdot 5}}{{3\cdot 7}}+\frac{{11}}{{21}}=\frac{{15}}{{21}}+\frac{{11}}{{21}}=\frac{{15+11}}{{21}}=\frac{{26}}{{21}}$

$\displaystyle 2)\;\;\frac{2}{7}\div\frac{{26}}{{21}}=\frac{2}{7}\cdot\frac{{21}}{{26}}=\frac{2}{7}\cdot\frac{{7\cdot 3}}{{2\cdot 13}}=\frac{3}{{13}}$

Answer 2

1) 5/7+11/21=1целая 5/21
2) 2/7 : 1 целая 5/21= 3/13