Update exercise, teaching time

Chris Erdmann · web-flow · commit 303b3eefea6b · 2019-06-23T11:58:49.000-04:00
diff --git a/_episodes/10-extra-challenges.md b/_episodes/10-extra-challenges.md
@@ -1,7 +1,7 @@
 ---
 title: "Extra challenges (optional)"
-teaching: 25
-exercises: 20
+teaching: 0
+exercises: 35
 questions:
 - "Are there extra challenges to practice translating plain English queries to SQL queries?"
 objectives:
