Answer:
210 yards
Explanation:
You are told that the two triangles (trails) are similar (since Perry wants to construct a similar trail to Hillsville's) this means that there is a scale factor meaning the length of one side of the Hillsville trail * scale factor = length of corresponding side of Perry's trail)
1. One side of the Hillsville trail that measures 400 yards corresponds to the 280 yard side of Perry's trail so the scale factor is
280/400 -> 7/10
2. Use the scale factor to find n since you know that the length of one side of the Hillsville trail * scale factor = length of corresponding side of Perry's trail
n = 300 * 7/10 -> n = 210