The football used in the game is made of black and white leather. The black leather is a regular pentagon, the white leather is a regular hexagon, and the sides of the black regular pentagon and the white regular hexagon are equal. The sewing method is: the 5 sides of each piece of black leather are sewed together with the sides of 5 pieces of white leather; among the 6 sides of each piece of white leather, 3 sides are sewn together with the sides of black leather, and the other The 3 sides are sewn together with the sides of other white leather. If there are 12 black regular pentagonal leathers on the surface of a football, then how many regular hexagonal leathers should the football have?
比赛用的足球是由黑、白两色皮子缝制的，其中黑色皮子为正五边形，白色皮子为正六边形，并且黑色正五边形与白色正六边形的边长相等．缝制的方法是：每块黑色皮子的5条边分别与5块白色皮子的边缝在一起；每块白色皮子的6条边中，有3条边与黑色皮子的边缝在一起，另3条边则与其他白色皮子的边缝在一起．如果一个足球表面上共有12块黑色正五边形皮子，那么，这个足球应有正六边形皮子多少块．
<gadget id="calculator">12 * 5</gadget>
<output>60</output>

<gadget id="calculator">60 / 3</gadget>
<output>20</output>

<result>20</result>