Assuming that the mural is a perfect square, therefore the formula for area is simply:
A = s^2
where A is area and s is the measure of the sides
Therefore from the formula, we can calculate the side lengths of the mural, s:
18 m^2 = s^2
s = sqrt (18 m^2)
s = 4.24 m
So the mural has a dimensions of 4.24 m by 4.24 m