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UKMT Grey Kangaroo, 2018

Algebra Difficulty 3.0 AMC 10/12 Find the answer United Kingdom

Wendy wants to write a number in every cell on the border of a table. In each cell, the number she writes is equal to the sum of the two numbers in the cells with which this cell shares an edge. Two of the numbers are given in the diagram. What number should she write in the cell marked $x$ ?

(A) $10$ (B) $7$ (C) $13$ (D) $-13$ (E) $-3$

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