Original: 150 T-shirts

New: 120 T-SHIRTS

Since the new amount is greater than the original, this is a percent of increase.

The amount of change = new T-shirts – original T-shirts.

The amount of change = .

Let r be the percentage of increase.

Use the original number, 150 as the base.

The percent proportion is

To solve for r, first find the cross products.

                                   (Multiply: )

                     (Divide each side by 150)

                                           (Cancel common terms)

                                       (Divide: )

The percentage of decrease by .

The percent of change is a percent of decrease.The percentage of decrease by .