A= \(\dfrac{1993\left(1994+1\right)}{1995\left(1992+1\right)}\)=1

B=\(\dfrac{399\left(45+55\right)}{1995\left(1996-1991\right)}\)=\(\dfrac{399.5.100}{399.5.5}\)=100

C=\(\dfrac{1996.1994+1996-996}{1000+1996.1994}\)=1

\(\frac{1995.1993-18}{1993.1994+1975}=\frac{\left(1994+1\right).1993-18}{1993.1994+1975}\)

                                          \(=\frac{1994.1993+1993-18}{1993.1994+1975}=\frac{1994.1993+1975}{1993.1994+1975}=1.\)

\(\frac{1995\cdot1993-18}{1993\cdot1994+1975}\)

\(=\frac{\left(1994+1\right)\cdot1993-18}{1993\cdot1994+1975}\)

\(=\frac{1994\cdot1993+\left(1993-18\right)}{1993\cdot1994+1975}\)

\(=\frac{1994\cdot1993+1975}{1993\cdot1994+1975}\)

\(=1\)

\(\frac{1994.1993-1992.1993}{1992.1993+1994.7+1986}\)\(=\frac{\left(1994-1992\right).1993}{1992.1993+1992.7+2.7+1986}\)\(=\frac{2.1993}{1992.\left(1993+7\right)+14+1986}\)

\(=\frac{2.1993}{1992.2000+2000}\)\(=\frac{2.1993}{2000.\left(2000+1\right)}\)\(=\frac{2.1993}{2000.2001}\)\(=\frac{2.1993}{2.1000.2001}\)\(=\frac{1993}{1000.2001}=\frac{1993}{2001000}\)

\(\frac{1994.1993-2}{1992+1992.1994}=\frac{1994.1992+1994-2}{1992+1992.1994}=\frac{1994.1992+1992}{1992+1992.1994}=1\)

    \(\frac{1994.1993-2}{1992+1991.1994}\)

= \(\frac{1994.1992-1994-2}{1992-1992.1994}\)

= \(\frac{1994.1992-1992}{1992-1992.1994}\)

=    \(1\)

\(\frac{4}{5×8}+\frac{4}{8×11}+\dots+\frac{4}{47×50}\)