The triangle below has a total perimeter of 450 cm: picture of a triangle with sides 128 and 150. third side unknown write an equation and solve it to find the length of the longest side of the triangle.

Mrs. avila is buying a wallpaper border to go on all of her kitchen walls. she wants to buy 5 extra feet of wallpaper border than she needs to be sure she has enough. she buys 55.5 feet of the border. the store owner selling the border uses the width of mrs. avila's kitchen to determine that the length of her kitchen must be 14.5 feet.