The school bought 4 tables and 5 chairs, which cost 450 yuan. The price of a table and 5 chairs is exactly the same. How much is the unit price of each chair?
学校买来4张桌子和5把椅子，共用了450元．一张桌子和5把椅子的价钱正好相等．每把椅子的单价是多少元？
<gadget id="calculator">4 * 5</gadget>
<output>20</output>

<gadget id="calculator">20 + 5</gadget>
<output>25</output>

<gadget id="calculator">450 / 25</gadget>
<output>18</output>

<result>18</result>