Basically, the same way that you solve equations that have variables only on one side. The general idea is that you can add, subtract, multiply and divide both sides of the quantities by the same...
you need to get all the vairables on one side. say the problem is 2x+3=x+5 then you need to put the x on the right side of the = to the left. when you do that it switches the positive x to negitve....
If you encounter an equation with variables on both sides, the here's what you need to consider. 1) If you have to, use the distributive law/property. 2) After that, you need to combine like terms....