Answer:
5 units.
Explanation:
1. Since all sides of a square have the same measurement, that would mean they have the same length. Using the perimeter equation of a square which is l + l + l + l = perimeter, the algebraic equation to find the length would be 4l = 20 since we substitute the unknown length as l.
2. In order to find out the length using 4l = 20, both sides need to be divided by 4 to get the variable by itself, resulting in l = 5 units as 20/4 = 5.