If the price of a textbook is 40 before tax is added on and tax is 10, what will the final price of the textbook be?

To calculate the final price of the textbook, you need to add the tax to the original price. The original price of the textbook is $40. Since the tax is 10 units (which we can assume is also in dollars), you simply add that to the original price.

So the calculation will look like this:

Final Price = Original Price + Tax

Final Price = $40 + $10 = $50

Therefore, the final price of the textbook after including tax will be $50.