The school bought 4 tables and 8 chairs for a total of 540 yuan. The price of a table and 3 chairs is exactly the same. How much does it cost to buy a set of tables and chairs?
学校买来4张桌子和8把椅子，共用540元，一张桌子和3把椅子的价钱正好相等，买一套桌椅要花多少元．
<gadget id="calculator">3 * 4</gadget>
<output>12</output>

<gadget id="calculator">12 + 8</gadget>
<output>20</output>

<gadget id="calculator">540 / 20</gadget>
<output>27</output>

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

<gadget id="calculator">81 + 27</gadget>
<output>108</output>

<result>108</result>