What is the quotient of the difference between 870 and 840 divided by the sum of 1530 and 840?
870与840的差去除1530与840的和，商是多少？
<gadget id="calculator">1_530 + 840</gadget>
<output>2_370</output>

<gadget id="calculator">870 - 840</gadget>
<output>30</output>

<gadget id="calculator">2_370 / 30</gadget>
<output>79</output>

<result>79</result>