Hi!
So really focus on the fact that he started at $230, and then added an amount of money which we'll call x, which made his total equal $599.
Take the parts I put in bold, and write the equation.
$230 + x = $599
Now we need to find x.
Whatever we do to the equation, we do it to both sides.
Our goal is to isolate x on one side.
Subtract 230 from both sides.
$230 - $230 + x = $599 - $230
x = $369
The answer is A. $230 + x = $599 x = $369
Hope this helps! :)
-Peredhel