Some classes in the third grade of Xueersi participated in the spring outing. It is known that the number of people in each class varies. And the number of girls in each class is the number of boys in the class (8/19), the day before departure. Half of the children in one class did not go. And the children who don't go are all boys, so the number of all girls is the remaining boys (16/35). How many classes are there in total?
学而思三年级有一些班级参加春游．已知每个班的人数相间．且每班的女生人数是该班男生人数的(8/19)，出发前一天．其中一个班有一半的孩子不去了．而且不去的孩子都是男生，于是全体女生人数是剩余男生的(16/35)．问一共有几个班？
<gadget id="calculator">16 / 35</gadget>
<output>16/35 = around 0.457143</output>

<gadget id="calculator">8 / 2</gadget>
<output>4</output>

<gadget id="calculator">(16/35) * 4</gadget>
<output>64/35 = around 1.828571</output>

<gadget id="calculator">19 / 2</gadget>
<output>19/2 = around 9.5</output>

<gadget id="calculator">(16/35) * (19/2)</gadget>
<output>152/35 = around 4.342857</output>

<gadget id="calculator">(64/35) + (152/35)</gadget>
<output>216/35 = around 6.171429</output>

<gadget id="calculator">(16/35) * 19</gadget>
<output>304/35 = around 8.685714</output>

<gadget id="calculator">(304/35) - 8</gadget>
<output>24/35 = around 0.685714</output>

<gadget id="calculator">(216/35) / (24/35)</gadget>
<output>9</output>

<result>9</result>