input: Write a function to find pairs of numbers in an array that sum up to a given value.
  assert equalSums([1, 2, 3, 4, 5, 6], 7) == [[1, 6], [2, 5], [3, 4]]
  assert equalSums([0, -1, 2, -3, 1], -2) == [[0, -2], [-1, -1]]
  assert equalSums([10, 20, 10, 40, 50, 60, 70], 50) == [[10, 40]]
output: def equalSums(arr, target):
      result = []
      seen = set()
      for number in arr:
          complement = target - number
          if complement in seen:
              result.append([complement, number])
          seen.add(number)
      return result