Fix FN3 description (#536)

Co-authored-by: Drew Lewis <[email protected]>

source/precalculus/exercises/bank.xml

@@ -93,7 +93,7 @@
             <slug>FN3</slug>
             <path>outcomes/FN/FN3</path>
             <description>
-                Use the graph of a function to find the domain and range in interval notation, the <m>x</m>- and <m>y</m>-intercepts, the maxima and minima, and where it is increasing and decreasing using interval notation.
+                Use the graph of a function to find the domain and range in interval notation, the x- and y-intercepts, the maxima and minima, and where it is increasing and decreasing using interval notation.
             </description>
         </outcome>