input: def linear_eq(a: int, b: int, c: int) -> float:
      """ Calculate the objective function of a linear equation of the form ax + by = c.
      >>> linear_eq(3, 5, 7)
      8.0
      """
output:     if a == 0 and b == 0:
          raise ValueError("Both coefficients a and b cannot be zero.")
      if a == 0:
          return c / b
      if b == 0:
          return c / a
      return (c - b) / a