We know that a number must be decreased by four. Let's break it up a little.
Nine times <em>some </em>number. We don't know what nine will be multiplied by, so we will just write a placeholder number: x. This number will be multiplied by nine. So it will turn into 9x.
We must decrease (subtract) from this by four. Subtracting 9x by four can be written as 9x - 4.
4 is equal to 1.75. I would plot 1.5 and 1.75 between 1 and 2, but 1.75 would be closer to 2. Since 1.75 is further to the right, it is greater than 1.5.