The dimensions of the quilts are increased by 25%, which means each dimension is increased by a factor 1.25. The area, or amount of material used to make each quilt is 1.25²=1.5625. This means that 56.25% more material is needed to make one quilt. To make 8 quilts we need 8 times as much material as we do for one quilt=12.5 times as much (1250%).
We can express these in two equations. If A is the area or amount of material used to make one quilt, then the new area X=1.5625A and the total T for 8 quilts is T=8X, or T=12.5A.