Since 9 is 3 times the denominator of the first ratio, multiply the numerator of the first ratio by 3 to get the numerator of the second ratio. The amount of pepper is 3/4 teaspoon.
To get this, you divide the smaller number by the larger one and get 0.5882... 500 is about 59% of 850, so to find the percent lost, you subtract that from 100 to get 41% decrease