A total of 50 students participated in sports activities. Among them, the ratio of those who can skip rope to those who cannot skip rope is 4:1, and the ratio of those who can kick shuttlecock to those who cannot kick shuttlecock is 3:2. There are 25 students who can do both kinds of sports. How many students do not know the project?
共有50个同学参加体育活动，其中会跳绳与不会跳绳的人数比是4：1，会踢毽子与不会踢毽子的比是3：2，两种项目都会的有25个同学，两种项目都不会的有多少个同学？
<gadget id="calculator">4 + 1</gadget>
<output>5</output>

<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">50 * (4/5)</gadget>
<output>40</output>

<gadget id="calculator">3 + 2</gadget>
<output>5</output>

<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">50 * (3/5)</gadget>
<output>30</output>

<gadget id="calculator">30 - 25</gadget>
<output>5</output>

<gadget id="calculator">40 + 5</gadget>
<output>45</output>

<gadget id="calculator">50 - 45</gadget>
<output>5</output>

<result>5</result>