Pls help me do last question, step by step for understanding

Let's ignore the four corners for now.

Along the top, the length is 145 cm. Each tile is 25 mm, which is equivalent to 2.5 cm. So she'll need 145/2.5 = 58 tiles across the top

Similarly, she'll also need 58 tiles across the bottom as well because that length is also 145 cm.

Along the left side, she'll need 75/2.5 = 30 tiles and the right side is the same story.

So far we calculate 58+58+30+30 = 176 tiles

Add in the four corners to get 176+4 = 180 tiles total

A quicker method is to divide the perimeter (440 cm) over the side length of each tile (2.5 cm) and we get 440/2.5 = 176, which represents the number of tiles along the top, bottom, left and right sides. Again we're ignoring the corners. So we'll have to add them back in to get 176+4 = 180.