Last year, Hongxing Primary School had 1,440 students, of which the ratio of male to female students was 7:5. This year, the number of female students increased by 20% compared with last year, and there are 78 fewer than male students. How many percent has the number of male students in Hongxing Primary School decreased this year compared to last year?
红星小学去年有学生1440人，其中男女生人数的比是7：5，今年女生人数比去年增加20%，还比男生少78人，今年红星小学的男生人数比去年减少了百分之几？
<gadget id="calculator">7 + 5</gadget>
<output>12</output>

<gadget id="calculator">7 / 12</gadget>
<output>7/12 = around 0.583333</output>

<gadget id="calculator">1_440 * (7/12)</gadget>
<output>840</output>

<gadget id="calculator">5 / 12</gadget>
<output>5/12 = around 0.416667</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_440 * (5/12) * (6/5)</gadget>
<output>720</output>

<gadget id="calculator">720 + 78</gadget>
<output>798</output>

<gadget id="calculator">840 - 798</gadget>
<output>42</output>

<gadget id="calculator">42 / 840</gadget>
<output>1/20 = around 0.05</output>

<result>1/20 = around 0.05</result>