Explanation:

- Total Cost (TC) is the sum of Total Fixed Cost (TFC) and Total Variable Cost (TVC).

- Option 1: TC = TFC x TVC

- This is incorrect because multiplying costs doesn't logically add up to the total cost in economics.

- Option 2: TC = TFC / TVC

- Dividing the fixed cost by the variable cost would not give the total cost.

- Option 3: TC = TFC + TVC

- This is correct. Total cost is literally the sum of fixed and variable costs.

- Option 4: TC = TFC - TVC

- This would mean subtracting variable costs from fixed costs, which isn’t a standard measure of total costs.