There are 28 more girls than boys participating in the mathematics competition. All the boys get excellent, but only 75% of girls get excellent. A total of 42 boys and girls get excellent. How many girls participate in the competition?
参加数学竞赛的女生比男生多28人，男生全部得优，女生只有75%得优，男、女生共42人得优，参加竞赛的女生有多少人？
<gadget id="calculator">70 / 1.75</gadget>
<output>40</output>

<result>40</result>