input: from typing import Tuple
  
  def linear_eq(a: float, b: float, c: float) -> float:
      """ Calculates the objective function of a linear equation ax + by = c.
      >>> linear_eq(3, 5, 7)
      0.0
      >>> linear_eq(2, 2, 4)
      0.0
      """
      x = 1
      y = 1
      return a*x + b*y - c
output:     if a*x + b*y == c:
          return 0.0
      else:
          return a*x + b*y - c