diff --git a/lesson-templates/lesson-07-optionals.tm b/lesson-templates/lesson-07-optionals.tm
index e23c4a3..4dc33e1 100644
--- a/lesson-templates/lesson-07-optionals.tm
+++ b/lesson-templates/lesson-07-optionals.tm
@@ -18,7 +18,10 @@ func main():
     >> y
     = ???
 
-    # Some functions return optional values:
+    # Some functions return optional values.
+    # Int.parse(text:Text -> Int?) is a function that returns
+    # an integer value found in the text, or `none` if no integer
+    # is found.
     >> Int.parse("123")
     = ???
     >> Int.parse("blah")
diff --git a/lesson-templates/lesson-16-reducers.tm b/lesson-templates/lesson-16-reducers.tm
index 7324882..3fc1c0b 100644
--- a/lesson-templates/lesson-16-reducers.tm
+++ b/lesson-templates/lesson-16-reducers.tm
@@ -28,4 +28,4 @@ func main():
     = ???
 
     >> (+: i for i in 10 if i:is_prime())!
-    = 0
+    = ???