One of a pentagon's sides is 3 feet longer than the other. If the perimeter of the pentagon is 128m, how long is the longest side?

Answer 1

Your opening sentence is not clear.
Are you saying that 4 of the sides are equal and one is 3 feet longer?
If that is the case, let each of the equal sides be x
then the longer side is x+3, and

x + x + x + x + x+3 = 128
5x+3=128
5x=125
x=15
longer side is 18, the others are 15

Answer 2

25+25+25+25+25+28=128

Answer 3

minus one of those 25

Answer 4

Reiny did it right except i x=25 not 15

Answer 5

of course 125/5 = 25 , silly of me