Answer:
5 ft
Explanation:
Since we have a rectangle, we know for sure that perimeter = double the width and double the height. Algebraically, that looks like:
P = 2W + 2H
Let's sub in the given values, P and W:
18 = 2(4) + 2H
Now, let's solve for the height, H:
18 = 8 + 2H
10 = 2H
10/2 = H
5 = H
I hope this helps!