A set of storybooks was first published in year x, and then it will be published every two years. The sum of the years of the first three publications is 6018. Please use equations to express the equivalence relationship in the question.
一套故事书第一次是在x年出版的，以后每过两年出版一次，前三次出版的年代和是6018，请用方程表示题中的等量关系．
<gadget id="calculator">6_018 - 2 - 2 - 2</gadget>
<output>6_012</output>

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

<gadget id="calculator">6_012 / 3</gadget>
<output>2_004</output>

<result>2_004</result>