Left, Right, Up, Down

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Across
  1. 2. For x - 3y = -7 and 3x + y = 9, this is x (Right to Left).
  2. 4. This superhero might be known as Arachnidman.
Down
  1. 1. Solve 3x - 5(2x + 7) = 18 - 3x - 1 (Down to Up).
  2. 3. For x - 3y = -7 and 3x + y = 9, this is y.