5 times a number plus the product of 4 and 5, the sum is 80, find this number.
一个数的5倍加上4与5的积，和是80，求这个数．
<gadget id="calculator">4 * 5</gadget>
<output>20</output>

<gadget id="calculator">80 - 20</gadget>
<output>60</output>

<gadget id="calculator">60 / 5</gadget>
<output>12</output>

<result>12</result>