In order to find the length and width values of the large poster we first need to find the width of the smaller poster since we are already given the length. Since we are also provided with the perimeter we can add the length twice and subtract it from the perimeter which would give us the value of both width sides of the rectangle, then we simply divide by 2 to get the value of the individual width.
10ft = 3ft + 3ft + w + w
10ft = 6ft + 2w
4ft = 2w
2ft = w
Since the larger poster is 3 times as big for the length and the width we simply multiply the smaller poster's length and width by 3...
L = 3 * 3 = 9ft
W = 2 * 3 = 6ft
Finally, we can see that the Larger poster is 9ft long by 6ft wide
