For the answer to the question above,
Let x = the length of the first piece
Then 3x = length of the second piece
And 5x + 2 = length of the third piece
Now, add all three of these together and set equal to 47:
x + 3x + (5x + 2) = 47
Now combine all the like terms and solve for x. Then use that value to find the length of the third piece.