Given,
The initial sale is 15.
The rate of increase of sale per week is 18 %.
The final sale is 1000.
The week at which the sales exceeds 1000 is:
![\begin{gathered} 1000=15*(1+(18)/(100))^t \\ (1000)/(15)=((118)/(100))^t \\ (200)/(3)=(1.18)^t \\ log\text{ \lparen}(200)/(3))=t\text{ log\lparen1.18\rparen} \\ t=25.37 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/gjr8j6wxjht6t7za0hl1mz8ihmoyi2rvgn.png)
The sales of the business reach to 1000 in 25th week.
Hence, the sales of the business exceed to 1000 in 26th week.