Let the number be X Decreasing 2 from XX - 2 = 80 x (1/X)X^2 - 2X = 80X^2 -2x -80 = 0(X-10)(X+8) = 0x=10,-8X has two values, but among the given options X value should be 10
Converting each of the given fractions into decimal form, we get,5/6 = 0.838/15 = 0.532/3 = 0.663/4 = 0.754/5 = 0.86/7 = 0.85Clearly, 0.85 does not lie between 0.83 and 0.53Hence the required fraction is 6/7.