Question 1115472
the house is priced at 150,000


20% off becomes 150,000 - .2 * 150,000 which becomes 150,000 * (1 - .2) which becomes 150,000 * .8 which is equal to 120,000.


the house is now priced at 120,000.


an additional 10% off becomes 120,000 - .1 * 120,000 which becomes 120,000 * (1 - .1) which becomes 120,000 * .9 which is equal to 108,000.


you could have gone there more directly by just taking 150,000 * .8 * .9 = 108,000


the combined discount becomes (150,000 - 108,000) / 150,000 = .28 = 28%.