Answer:
The length would be 1.5x + 5.
Explanation:
So first with this, note that 2 length + 2 height gives the perimeter of the rectangle.
Given this:
2(1/2x + 4) + 2(?) = 4x+18
x+8 + 2(?) = 4x+18
2(?) = 3x+10
? = 1.5x+5
1.5x + 5 = 1.5x + 5
The length would be 1.5x + 5.
To double check, by plugging in 1.5x + 5 back into the equation for the perimeter, you will get the same perimeter:
2(1.5x + 5) + 2(1/2x+4) = P
3x+10 + x+8 = P
4x + 18 = P