18 - ln(3-x)=0

18 - ln(3-x)=0   add ln(3-x) to both sides

18 = ln(3-x)      exponentially, this says

e^18 = 3 -x      add x to both sides and subtract e^18 from both sides

x = 3 - e^18 ≈  -65,659,966.137