Sum of the decimal places = 7 .Since the last digit to the extreme right will be zero ( 5 * 4 = 20), so there will be 6 significant digits to the right of the decimal point....
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
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