fix a tour typo

site/text/tour.md

@@ -76,7 +76,7 @@ If you like, you can put values on the stack first, then operate on them.
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-For math functions where the order matters, like [subtract](/docs/sub) and [divide](/docs/div), what would normally be the second argument is instead the first. This is so you can think of fragments like `¯2` as a single unit.
+For math functions where the order matters, like [subtract](/docs/sub) and [divide](/docs/div), what would normally be the second argument is instead the first. This is so you can think of fragments like `-``2` as a single unit.
 
 If you want them to work the other way, you can use [flip](/docs/flip), which swaps the top two values on the stack.