Every year, the price of the smartphone is the [tex] 67\% [/tex] of the price of the previous year (since we lose the [tex] 33\% [/tex], we remain with the [tex] 67\% [/tex]).
Since [tex] 67\% [/tex] can be written as [tex] \frac{67}{100} [/tex], the price after one year will be
[tex] 243 \cdot \frac{67}{100} = 162.81 [/tex]
After two years, the price is the [tex] 67\% [/tex] of the price after one year:
[tex] 162.81 \cdot \frac{67}{100} = 109.08[/tex]
And so on: after three years we have
[tex] 109.08 \cdot \frac{67}{100} = 73.08 [/tex]
So, the answer is somewhere between three and four years.
