Question

solve for y given that the perimeter of the triangle is 30 miles.

Explanation:

Step1: Recall perimeter formula

The perimeter $P$ of a triangle is the sum of its side - lengths. So, $P = 9 + 9+y$.

Step2: Substitute the given perimeter value

We know that $P = 30$. So, $30=9 + 9+y$.

Step3: Simplify the right - hand side

First, add 9 and 9: $9 + 9=18$. The equation becomes $30=18 + y$.

Step4: Solve for y

Subtract 18 from both sides of the equation: $y=30 - 18$.

Answer:

$y = 12$