Plz see picture and question attached

The answer is 16m² because the square root of 81 is 9 meaning both width and height of the patio are 9. to find the height of the square patch you do 9 - 5 = 4
because it is square, meaning the width and height are the same, so therefore the width is also 4. to get the area of a square of rectangle, you times the width by the height. 4 × 4 = 16. so the answer is 16m² because the unit is metre so we write m²