you start by taking the 2.5 over to the other side. This is a positive number so when you take it over it will become a negative.
2.5-0.25x = -3
-0.25x =-3-2.5
-0.25x=-5.5
now -0.25 is being multiplied to x, when you take it over to the other side, it becomes divide.
-0.25x = -5.5
x = -5.5/-0.25
x = 22