I would be careful. The problem says the rectangle's perimeter is equal to 30.
That means all the sides added up are equal to 30.
That one side is 6 in. That means the opposite is also 6.
6+6= 12
Subtract from 30 (the perimeter)
30-12= 18
Divide 18 by 2 for the remaining two sides (since the other two sides are equal)
18/2= 9
The width is equal to 9.
We can also find the area.
Area= length*width
6 (the length) * 9 (the width)= 54
I hope this helps!