To buy a new computer for $2100. The computer decreases by 50% annually. When with the computer have a value of $600?

The computer will never reach an exact value of $600 dollars if the price only decreases annually, but after 2 years it will reach $525

The question at hand here is 2100:2^ * = 600. We need to find x. It can be done with trial and error, by just replacing x with different numbers until you get 600. Another way to work it out would be with logarithms, but by the way the question is phrased without an integer number, logarithms might be a bit too far for this.