imo it's better to defeat Shinra early in Ch 3, bc the ladyluck ds has double exp, which makes leveling so much faster.
Anyway, here's an even simpler (maybe too simple...don't laugh!) method to defeating Shinra easily (this can be used in either chapter, though for Ch 5, since the quota is larger, I might recommend using a 4 coin count instead of a 3 coin count).
Easy method to beat Shinra without the timer:
When the pause screen comes on that says Turn:1, DON'T press x yet. Keep the screen paused, then, write down the numbers 2-9 on a piece of paper. These numbers represent all the possible core numbers that might show up. Just go down the line, and make one possible equation for each possible core number. You make the equations by looking at all the coins on screen (duh).
Each equation should use three coins exactly. One gold coin from the middle, and two silver ones from the outer edges. I won in 9 turns using 3 coins in each turn, so just make sure every equation uses exactly 3 coins.
Just keep repeating this entire process before every turn, when the pause screen comes up. If you want it to go by faster, you should do a 4 coin count instead of 3.
To help you even more, use a calculator to keep adding up 3 coins and seeing if they make mulitples of whatever possible core number you're working on. Also, if you have trouble remembering your multiples, just get a multiplication chart and refer to that. As long as Shinra's core number doesn't keep giving you ones, you should be able to get ladyluck ds in no time.
This method may take longer, but it is a no-fail and no-stress method.
