Go to each side of the equal sign and combine your x's (or variables of like kind) then your numbers (constants) without x's (or other variables of like kind) and use the sign in front of the term, and when there is no sign, it may be positive or + in most cases! How does this answer your question? If you have two terms one has an "x" and the other just a number, alone those are not "like kind" (one is a constant(for example "5") and the other a variable(Ffor example "x")) and should not be combined because one is part of the variables and the other is part of the constants. When I say "combine" this is where you "add or subtract" those variables or like terms. In the example you provided the variable with the equal sign, erasing the rest of the problem reads "2x+3x=" Notice how they are both on the same side of the equal sign, in this case you just do as it reads "2x+3x=" or "5x=" do not forget to keep that equal sign so you can determine where the rest of the terms go. Sometimes you will encounter variables or other terms on the other side of the equal sign, in a case like this simply combine like terms on one side of the equal sign and then do the same to the other, no particular order but some say it is easier to use a method or pattern. EXAMPLE 2x+5x+5+2= -5x-13x+32. Do not get scared it only looks more challenging then it is. IF you picture your variables with everything else other than the equal sign erased you will have "2x+5x=-5x-13x" I know this will not work out as a problem, just use it as a visual. and combine. You should get "7x=-18x". You could go even further and move your x's to one side or just wait until that step. In the example I provided it requires an extra step that some call reversing/negating the terms and others in your book call it something similiar. Just a thought!!
Lastly, move your variables to one side of the equal sign and your constants to the other side of the equal sign. It really does not matter what side unless you see an easy way to solve, but variables must always be on that one side of the equal sign you pick and constants on the other side of the equal sign. Usually 25x=25 or x=1, and 25=x or 1=x no matter what order if you do not mind the multiplication rule of multiplying negatives and positives. that is where you create you easy method.