How do you solve ln e^x -ln e^3 = ln e^9?

If you use the properties of logarithms you will need to refer to these:
OR
##lne^z = z##
where ##a## and ##b## are constants ##e = 2.718281828cdots## and ##z## is either a constant or a variable. Therefore we can do this:
##lne^x – lne^3 = lne^9##
##lne^x = lne^9 + lne^3##
##xcancel(lne) = 9cancel(lne) + 3cancel(lne)##
##color(blue)(x) = 9 + 3 = color(blue)(12)##