\(=\dfrac{1993}{7+1986}=\dfrac{1993}{1993}=1\)
c= \(\dfrac{1994x1993-1992x1993}{1992x1993+1994x7+1986}\)
c=\(\dfrac{1993x\left(1994-1992\right)}{1992x1993+1994x7+1986}\)
c= \(\dfrac{1993x2}{1992x1993+1994x7+1986}\)
c=\(\dfrac{2}{1992x1+1994x7+1986}\)
c=\(\dfrac{1}{13903161}\)