The ratio of the number of boys to girls in the fifth grade of a certain school is 5:4. There are 20 more boys than girls. How many girls are there?
某校五年级男、女生人数的比是5：4，男生比女生多20人，女生有多少人？
<gadget id="calculator">5 - 4</gadget>
<output>1</output>

<gadget id="calculator">20 / 1</gadget>
<output>20</output>

<gadget id="calculator">20 * 4</gadget>
<output>80</output>

<result>80</result>