A phone factory makes twice as many phones as last year. Last year's production was 5000 phones. If a quarter of this year's production is sold, how many phones are left in the factory? Let's answer step by step:
This year's total production is 5000 * 2 = 10000 phones. A quarter of this year's production is 10000 / 4 = 2500 phones. The number of phones left after selling a quarter of the production is 10000 2500 = 7500 phones. The answer: 7500.