Answer:
See below.
Explanation:
First, two of you hold the string at its opposite ends. Then you come together. the third friend will then grab the string approximately at it's centre and walk away from you both loosely holding the string and adjusting his hold until both halves of the string are taut. He will now be holding the middle of the string and the 2 other friends walk away in opposite directions with the string kept taut. When they are at the farthest point they can travel the 3 friends are now equal distances apart.