What evidence is there that the colonists had already unsuccessfully voiced concerns to the king?

Answer 1

What does your text say? Did the Continental Congress have a representative in London to express grievances? Did the Declaration of Independence enumerate attempts to petition the King and Parliament? What other evidence does your text suggest or describe?

Answer 2

Here are several sites that should help you answer this question. If one doesn't give you the information you want or need, try another one until you find what you want.

http://www.bing.com/search?q=grievances+against+the+king+and+parliament+expressed+by+american+colonists&form=EDGNTC&qs=PF&cvid=18dd65b3cbd1407992d855f607dc25d5&pq=grievances+against+the+king+and+parliament+expressed+by+american+colonists