input: def linear_eq(a: int, b: int, c: int) -> int:
      return a*x + b*y - c
  
  # For example:
  result = linear_eq(3, 5, 7)
  print(result)
output:     if a == 0 and b == 0:
          return 0 if c == 0 else None
      elif a == 0:
          return c // b if c % b == 0 else None
      elif b == 0:
          return c // a if c % a == 0 else None
      else:
          for x in range(c // a + 1):
              if (c - a * x) % b == 0:
                  return x
          return None