part1/Relations: Fix Typo

"form `m ≤ n`" -> "from `m ≤ n`"

src/plfa/part1/Relations.lagda.md

@@ -161,7 +161,7 @@ Chapter [Decidable]({{ site.baseurl }}/Decidable/).
 ## Inversion
 
 In our defintions, we go from smaller things to larger things.
-For instance, form `m ≤ n` we can conclude `suc m ≤ suc n`,
+For instance, from `m ≤ n` we can conclude `suc m ≤ suc n`,
 where `suc m` is bigger than `m` (that is, the former contains
 the latter), and `suc n` is bigger than `n`. But sometimes we
 want to go from bigger things to smaller things.