So, let the width be x. The lenght will be 3 inches more than five times the width: 3 +5x. The perimeter is 66 in.
So, the width is x and the lenght is 3+5x. The perimeter will be:
(x+3+5x)*2=66
(6x+3)*2=66
12x+6=66
12x=60
x=5 = width
So the lenght is 3+5*5 = 28 = lenght
The lenght of the signs is 28 in and the width is 5 in.