Answer:
The length of side of original square is: 20 inches
Explanation:
Let x be the length of side of original square
Then x+5 will be the side of new square
Th formula for perimeter is:

As we know the perimeter of the new square we can use the perimeter to find the value of x

The value of x is 20 inches.
Hence,
The length of side of original square is: 20 inches