What is the value of
x/3y, when x = 18 and y = 3?

X/3y has the value of 2. Here's the work x=18 so it's 18/3y and y=3 so you add the three in the place of y and multiply. 18/3(3) which gives you 18/9 and 18 divided by 9 is 2.

In this problem it decreased 20%

The number is 80 because every number is multiplied by 2