If the length is 1¼ times the width we can work out the area in terms of the width: 1×1¼=5/4 square widths.
So we divide the area by 5/4 which is the same as multiplying it by 4/5: 4/5×180=144 sq in. This is square widths, so it’s the same as a square where the side of the square is one width. That means the side of the square is 12in because 12×12=144. If the width is 12in then the length is a quarter more, which is 3in added to 12=15in. The dimensions are length=15in and width=12in. 15×12=180 sq in.