An 8-inch pizza has a radius of 4 inches.
A 12-inch pizza has a radius of 6 inches.
Area of first pizza: \(\pi r^2\)\(= 16\pi\)
Area of second pizza: \(\pi r^2=36\pi\)
Calculation of percentage: \(\frac{36-16}{16} \times 100 = 125%\)%
Therefore, the area is increased by \(125\)%