Final answer:
To calculate the expression for the third side of the triangular park, subtract the given sides from the total perimeter, resulting in the expression 9x - 1.
Step-by-step explanation:
The expression for the third side of the triangular park can be found by knowing that the perimeter of a triangle is the sum of its three sides. We are given the perimeter as 16x+3 and two of the sides as 2x+5 and 5x-1. To find the third side, you subtract the lengths of the known sides from the total perimeter.
Therefore, the third side (let's call it S) can be calculated as follows:
Perimeter = First Side + Second Side + Third Side
16x + 3 = (2x + 5) + (5x - 1) + S
16x + 3 = 7x + 4 + S
S = 16x + 3 - 7x - 4
S = 9x - 1
This means the expression for the third side is 9x - 1.