Solve the equation: 5x-50+7x=790.
解方程：5x-50+7x=790．
<gadget id="calculator">50 + 790</gadget>
<output>840</output>

<gadget id="calculator">5 + 7</gadget>
<output>12</output>

<gadget id="calculator">840 / 12</gadget>
<output>70</output>

<result>70</result>