There are 840 pear trees in the orchard, and the number of pear trees is 30 less than twice that of peach trees. How many peach trees are there?
果园里有梨树840棵，梨树的棵数比桃树的2倍少30棵，桃树有多少棵？
<gadget id="calculator">840 + 30</gadget>
<output>870</output>

<gadget id="calculator">870 / 2</gadget>
<output>435</output>

<result>435</result>