[3.(1/4-1/5+1/7+1/11)] / [13.(1/4-1/5+1/7+1/11)]
=3/13
tk tui nha
\(\frac{3\left(\frac{1}{4}-\frac{1}{5}+\frac{1}{7}+\frac{1}{11}\right)}{13\left(\frac{1}{4}-\frac{1}{5}+\frac{1}{7}+\frac{1}{11}\right)}=\frac{3}{13}\)
\(\frac{3\left(\frac{1}{4}-\frac{1}{5}+\frac{1}{7}+\frac{3}{11}\right)}{13\left(\frac{1}{4}-\frac{1}{5}+\frac{1}{7}+\frac{1}{11}\right)}\)\(=\frac{3}{13}\)
\(\frac{\frac{3}{4}-\frac{3}{5}+\frac{3}{7}+\frac{3}{11}}{\frac{13}{4}-\frac{13}{5}+\frac{13}{7}+\frac{13}{11}}=\frac{3}{13}\)