Xiao Ming has to write 250 characters at home during the winter vacation. I wrote 15 letters every day in the first 10 days, and I plan to finish writing the rest in 5 days, so how many big characters do I need to write every day?
小明寒假在家要写250个大字．前面10天每天写了15个，余下的准备5天写完，那么每天需要写多少个大字？
<gadget id="calculator">15 * 10</gadget>
<output>150</output>

<gadget id="calculator">250 - 150</gadget>
<output>100</output>

<gadget id="calculator">100 / 5</gadget>
<output>20</output>

<result>20</result>