If this is meant to be ln(x) = 4*logx(e) (i.e. log to base x of e) then
ln(x) = logx(e4)
xln(x) = e4
Take log to base e of both sides
ln(xln(x)) = ln(e4)
ln(x)*ln(x) = 4
[ln(x)]2 = 4
ln(x) = ±2
x = e2 and x = e-2
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