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?
This year's total production is 5000 * 2 = 
<gadget id="calculator">5000*2</gadget>
<output>10_000</output>
10000 phones.
A quarter of this year's production is 10000 / 4 = 
<gadget id="calculator">10000/4</gadget>
<output>2_500</output>
2500 phones.
The number of phones left after selling a quarter of the production is 10000 - 2500 = 
<gadget id="calculator">10000-2500</gadget>
<output>7_500</output>
7500 phones.

<result>7_500</result>