<PRE><B>Question 35326</B>
log2 (5x+7) - log2 x = 2

log2(a) - log2(b) = log2 (a/b)

using the above identity
log2 ((5x+7)/x) = 2

log 2 to the base 2 is 1 i.e log2 2 = 1 
2 can be written as 2*1 = 2log2 (2) =  log2 (4)

log2 ((5x+7)/x) = log2 (4)

since the log on the right and the left side is with the same base
(5x + 7)/x = 4
5x + 7 = 4*x
x = -7</PRE>