The ratio of boys to girls in a certain school last year was 3:1. This year, the number of boys decreased by 12%, and the number of girls increased by 20%. So how many boys accounted for the total number of people in this year?
某学校上一年男生与女生人数的比是3：1，本年度男生减少了12%，女生增加了20%．那么在本年度中男生占全部人数的多少．
<gadget id="calculator">1 + 3</gadget>
<output>4</output>

<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">12 / 100</gadget>
<output>3/25 = around 0.12</output>

<gadget id="calculator">1 - (3/25)</gadget>
<output>22/25 = around 0.88</output>

<gadget id="calculator">(3/4) * (22/25)</gadget>
<output>33/50 = around 0.66</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 + (1/5)</gadget>
<output>6/5 = around 1.2</output>

<gadget id="calculator">(1/4) * (6/5)</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">(33/50) + (3/10)</gadget>
<output>24/25 = around 0.96</output>

<gadget id="calculator">(33/50) / (24/25)</gadget>
<output>11/16 = around 0.6875</output>

<result>11/16 = around 0.6875</result>