Marcie bought a 50 foot roll of packing tape she use two 8 5/6 foot lenghts how much take us left on the roll !

Every year, the price of the smartphone is the of the price of the previous year (since we lose the , we remain with the ).

Since can be written as , the price after one year will be

After two years, the price is the of the price after one year:

And so on: after three years we have

So, the answer is somewhere between three and four years.