In the Giant School, 105 boys and 75 girls participated in the mathematics competition, and 95 girls and 85 boys participated in the composition competition. It is known that a total of 280 students in the school participated in the competition, and the number of boys who only participated in the mathematics competition was the same as the number of girls who only participated in the composition competition. May I ask: How many girls are there who only participate in the math competition?
巨人学校有105名男生和75名女生参加数学竞赛，有95名女生和85名男生参加作文竞赛．已知该校一共有280名学生参加了竞赛，其中只参加数学竞赛的男生人数与只参加作文竞赛的女生人数相同．请问：只参加数学竞赛的女生有多少人？
<gadget id="calculator">75 - 35</gadget>
<output>40</output>

<result>40</result>