What is 7a - 3 = 3 + 6a

Firstly, you add 3 to both sides (as you've got to eliminate the -3), and this gives you;
7a=6+6a.
Then in order to get a alone, you need to subtract 6a from the right hand side (in order to counter balance) and this gives you;
1a=6
Therefore, a is equal to 6
Hope this helps :)