Lily is cutting a piece of yarn into 3 (three) pieces. The 2nd piece is 3 times as long as the 1st piece, while the 3rd piece is 6 centimeters longer than the 1st piece. When the yarn has a total length of 211 centimeters, calculate the length of the first piece.

(-3, 3)

Step-by-step explanation:

The points are easy to plot on a graph to see where the other endpoint should be.  See the attached image.

You can also look at the problem this way:

Start at the midpoint and go to the given endpoint, paying attention to how far right/left and up/down you go, a bit like following streets and avenues.

From (-1, 5) TO (1, 7), you go right 2, then up 2.  Now go back to the midpoint and reverse those two motions.

From (-1, 5) go left 2, then down 2.  You are at the other endpoint, (-3, 3).