<s>[INST] Finding all integer solutions of $\frac{1}{x} + \frac{1}{y} - \frac{1}{z} = \frac12$ If we have integers $x,y,z$ such that $x,y,z \ge 3,$ find all solutions to $$\frac{1}{x} + \frac{1}{y} - \frac{1}{z} = \frac12.$$

I was thinking of first expanding out this, and then simplifying from there, but the equation got very messy. Is there a better method?
 [/INST] WLOG let $x\leq y$. Then, we have that $x = 3$ because we are given that $x\geq 3$, and if $x\geq 4$, $\frac{1}{x}+\frac{1}{y}\leq \frac{1}{2}$.
Then, we must solve $\frac{1}{y}-\frac{1}{z} = \frac{1}{6}$. Note that $y = 3,4,5$ because they are the only values such that $y\geq 3$ and $\frac{1}{y}>\frac{1}{6}$. Then, we can go into casework:
For $y = 3$, we get $\frac{1}{z} = \frac{1}{6}$ and thus $z = 6$.
For $y = 4$, we get $\frac{1}{z} = \frac{1}{12}$ and thus $z = 12$.
Finally, for $y = 5$ we get $\frac{1}{z} =\frac{1}{30}$ and thus $z = 30$.
We must permute $x$ and $y$ when they are different to get all of the solutions because of the earlier WLOG.
Thus, the only solutions are $\boxed{(3,3,6),\  (3,4,12),\ (3,5,30),\ (4,3,12),\text{ and }(5,3,30).}$
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