In March, several teachers planted voluntary trees. If each tree planted 5 trees, and there were no one to plant 3 trees. If 3 of the female teachers planted 4 trees and the rest of the male teachers planted 6 trees, these saplings were just planted. How many teachers are there to plant trees?
3月份有几位老师去义务植树，如果每条种5棵，还有3棵没有人种，如果其中3位女教师各种4棵，其余男教师各种6棵，这些树苗正好种完，问有多少老师去植树？
<gadget id="calculator">6 * 3</gadget>
<output>18</output>

<gadget id="calculator">4 * 3</gadget>
<output>12</output>

<gadget id="calculator">18 - 12</gadget>
<output>6</output>

<gadget id="calculator">3 + 6</gadget>
<output>9</output>

<gadget id="calculator">6 - 5</gadget>
<output>1</output>

<gadget id="calculator">9 / 1</gadget>
<output>9</output>

<result>9</result>