Correct typo from nu13 to nu18 in L659

kakirastern · web-flow · commit 275bd8c45af2 · 2019-02-13T00:47:06.000+08:00
diff --git a/tutorials/notebooks/quantities/quantities.ipynb b/tutorials/notebooks/quantities/quantities.ipynb
@@ -635,7 +635,7 @@
    "outputs": [],
    "source": [
     "nu13 = lambda13.to(u.Hz)\n",
-    "nu18 = lambda13.to(u.Hz)"
+    "nu18 = lambda18.to(u.Hz)"
    ]
   },
   {
