Answer :

[tex]3^x-3^{x-1}=18\\\\3^x-3^x\cdot3^{-1}=18\\\\3^x-\frac{1}{3}\cdot3^x=18\\\\\frac{2}{3}\cdot3^x=18\ \ \ /\cdot\frac{3}{2}\\\\3^x=27\\\\3^x=3^3\iff x=3\\------------------\\4^x=4^3=64\leftarrow answer[/tex]
konrad509
[tex] 3^x - 3^{x-1} = 18\\ 3^x-3^x\cdot3^{-1}=18\\ 3^x(1-\frac{1}{3})=18\\ 3^x\cdot\frac{2}{3}=18\\ 3^x=27\\ x=3\\\\ 4^x=4^3=64 [/tex]

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