5x=7.3+4x
First, get all of the variables on one side. Do this by subtracting 4x from both sides. This removes 4x from the right side, since a number n-n is 0, and you don't need to write down adding 0.
5x-4x=7.3+4x-4x
5x-4x=7.3
You have now 5 of a number x, and 4 of a number x. Since you have 5 of something and 4 of the same something, just subtract. 5-4=1.
x=7.3
