The product of 3 times a number plus 5 times 2, the sum is 91, find this number.
3乘一个数的积加上2的5倍，和是91，求这个数．
<gadget id="calculator">2 * 5</gadget>
<output>10</output>

<gadget id="calculator">91 - 10</gadget>
<output>81</output>

<gadget id="calculator">81 / 3</gadget>
<output>27</output>

<result>27</result>