\(a,\dfrac{5\times6\times7\times8\times9\times10}{7\times8\times9\times10\times11}=\dfrac{5\times6}{11}=\dfrac{30}{11}\)
\(b,\dfrac{3\times145+3\times55}{6\times215+6\times85}=\dfrac{3\times\left(145+55\right)}{6\times\left(215+85\right)}=\dfrac{3\times200}{6\times300}=\dfrac{1}{2}\times\dfrac{2}{3}=\dfrac{1}{3}\)
\(c,\dfrac{21\times45}{9\times7\times5\times3}=\dfrac{7\times3\times9\times5}{9\times7\times5\times3}=1\)
\(d,\dfrac{2\times6\times11}{33\times24}=\dfrac{2\times6\times11}{3\times11\times6\times2\times2}=\dfrac{1}{6}\)
\(e,\dfrac{2\times3\times5}{70}=\dfrac{2\times3\times5}{2\times5\times7}=\dfrac{3}{7}\)
\(g,\dfrac{25\times8+25\times9+25-25\times5}{99+98+97+96}=\dfrac{25\times\left(8+9+1-5\right)}{390}=\dfrac{5\times5\times13}{13\times5\times6}=\dfrac{5}{6}\)
