A percent discount of 30%
Step-by-step explanation:
Since $129 represent 100% of the price, then the new price $90.30 represent 70 %
129 * 100 / 90.30 = 70 %
Since from the 100% of the price, it went to 70% of it, there was a discount of 30%
100 - 70 = 30%