This rule shows how we transition the x-coordinate and y-coordinate when finding B'.
In this rule, it shows us what to add/subtract from the x-value and y-value in the coordinate. We can see that it wants us to subtract 5 from the x-value (based on the "x - 5") and that it wants us to add 9 to the y-value (based on the "y + 9"). Based on this information, we can find B':
The "y-coordinate" of B' is 6.