There are 36 peach trees in the orchard, and the number of pear trees is twice that of peach trees. There are 18 fewer apple trees than the total number of peach and pear trees. How many apple trees are there?
果园里有36棵桃树，梨树的棵数是桃树的2倍，苹果树比桃树和梨树的总数少18棵，苹果树有多少棵？
<gadget id="calculator">36 * 2</gadget>
<output>72</output>

<gadget id="calculator">72 + 36</gadget>
<output>108</output>

<gadget id="calculator">108 - 18</gadget>
<output>90</output>

<result>90</result>