input: def calculate_objective_function(a: int, b: int, c: int) -> int:
      """Calculate the objective function for a linear equation of the form ax + by = c.
      Returns the result of a*x + b*y - c.
      >>> calculate_objective_function(3, 5, 7)
      15
      """
      return a*x + b*y - c
output:     x = 2
      y = 3
      return a*x + b*y - c