Help solving this easy algebra question

7x = 3x + 39

Solve for x

Please explain the answer too.
Thanks

to isolate x on one side, simply subtract 3x from both sides
7x-3x = 3x-3x+39
so 4x=39
then to get x alone you divide both sides by 4, since you only want the value of one x instead of 4x,
x=39/4
which happens to be, according to my calculator (or longhand division if you have a pencil and paper)...9.75
x=9.75

Why?

My answer:

http://imgur.com/gvaNP

I hope u can understand it.