UKMT Grey Kangaroo, 2023

Algebra Difficulty 1.0 Junior Find the answer United Kingdom

Werner wants to write a number at each vertex and on each edge of the rhombus shown. He wants the sum of the numbers at the two vertices at the ends of each edge to be equal to the number written on that edge. What number should he write on the edge marked with the question mark?

(A) $11$ (B) $12$ (C) $13$ (D) $14$ (E) $15$

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