There are 157 students in three classes in a certain school, and the number of boys in the three classes is equal. The boys in the first class account for the whole class (7/13), and the boys in the second class account for the whole class (4/7), so how many girls are there in the third class?
某校三个班学生共有157人，且三个班的男生人数都相等．第一班男生占全班的(7/13)，第二班男生占全班的(4/7)，那么第三班的女生有多少人．
<gadget id="calculator">157 - 52 - 49</gadget>
<output>56</output>

<gadget id="calculator">7 / 13</gadget>
<output>7/13 = around 0.538462</output>

<gadget id="calculator">52 * (7/13)</gadget>
<output>28</output>

<gadget id="calculator">56 - 28</gadget>
<output>28</output>

<result>28</result>