A way that trade barriers can affect you as a customer is by raising prices of the protected good and hurt foreign producers of the good who wish to export to the country.
Isn't one all the factories causing climate change? Am I right?
So first you do distributive property. Multiply everything inside by 3. So you will get 3*x = 3x and 3*4 = 12. Now that you did that you got rid of the parenthesis and you are left with
y=3x+12
The promontories that Bede describes in A History of the English Church and People are peaks of high coastal land.