1. 100 increased by 99%

2. 75 decreased by 80%

1. 199

2. 15

Step-by-step explanation:

1. To increase a number by a certain amount, you multiply the number by 0.99 and add it to the original number:

100 (0.99) = 99

100+99 = 199

2. To decrease a number by a certain amount, you can multiply the number by 0.80 then subtract it from the original number:

75 (0.80) = 60

75-60 = 15