log(A) means the power to which 10 must be raised to give A. log10^12 = 12 because the power to which 10 must be raised in order to get 10 raised to the 12th power is 12. log10^9 = 9 because the power to which 10 must be raised in order to get 10 raised to the 9th power is 9. log10^0.4 = 0.4 because the power to which 10 must be raised in order to get 10 raised to the 0.4th power is 0.4. [The above requires the same reasoning as "The city to which you must be in -- in order to be in Chicago -- is Chicago." :)] So If x=log10^12,y=log4^2Ślog10^9 and z=log10^0.4 find x-y-z becomes: If x=12,y=log4^2Ś9 and z=0.4 find x-y-z So x-y-z = 12-9Ślog4^2-0.4 = 11.6-9Ślog4^2 = ll.6-9Ślog16 = 11.6-9Ś1.204119983 = 0.762920153. Edwin