Locking a profit by hedging after the odds move

Earlier you backed outcome $X$ of a two-outcome event, staking $100 at decimal odds of $3.00$ (so you collect $300 if $X$ occurs, and lose your $100 otherwise). The market has since moved, and you can now back not-$X$ at decimal odds of $2.00$. You want to hedge so your net profit is the same whichever outcome happens — a locked profit. How many dollars should you now stake on not-$X$, and what is your guaranteed profit? Give the guaranteed profit (in dollars).