Square EFGH has side length GH = 21 cm (found from EB minus AE = 36 minus 15).<br><br>Perimeter of square EFGH = 4 x 21 = 84 cm.<br>Area of square EFGH = 21 x 21 = 441 cm&sup2;<br><br>Final Answer: Perimeter = 84 cm, Area = 441 cm&sup2;