Answer:
15 inches
Step-by-step explanation:
The perimeter is 3 times the side length. If the original side length is represented by s, we are told by the problem statement that ...
... 3(s +5 in) = 60 in . . . . an equation for the increased perimeter
... s +5 in = 20 in . . . . . . divide by 3
... s = 15 in . . . . . . . . . . . subtract 5 in
The original side length is 15 in.
