A computer companys featured laptop cost $800 last year. This year

Long/Proper solution-

Cost of the laptop last year = $800

Price this year = 15% less than the cost of last year = Cost of last year - 15% of cost of last year
=> price this year = \(800 - \frac{15}{100}*800\)
=> price this year = 800 - 120 = 680

Price next year = 25% more than the price this year = price this year + 25% of price this year
=> price next year = \(680 + \frac{25}{100}*680\)
=> price next year = 680 + 170 = 850

Therefore, answer is D

Short solution-

Percentages can be multiplied successively without having to worry about the intermediate result.

For further understanding of this please checkout the second topic (as mentioned in the content) in this post by Bunuel https://gmatclub.com/forum/percentages-interest-and-more-208098.html#p1596558

This provides us with a very handy method and one that every test taker should know. This will save significant time on such questions as can be seen from the current example- reducing time from 2 mins to under 10 secs.

Price next year = Price last year * change in price last year * change in price this year
=> price next year = 800 * 0.85 * 1.25
=> price next year = $850