Solve the equation: 3,130-x)=70+x.
解方程：3,130-x)=70+x．
<gadget id="calculator">390 - 70</gadget>
<output>320</output>

<gadget id="calculator">3 + 1</gadget>
<output>4</output>

<gadget id="calculator">320 / 4</gadget>
<output>80</output>

<result>80</result>