fix bug in Update ex1.py

Author: JohnM-TX

learntools/sql_advanced/ex1.py

@@ -80,10 +80,10 @@ def check(self, query):
         # check 2: calculated values
         # correct result
         correct_list = correct_answwer.loc[correct_answer["time_to_answer"].notna(), "time_to_answer"]
-        correct_number = correct_list.sum()/len(correct_list))
+        correct_number = correct_list.sum()/len(correct_list)
         # submitted value
         submitted_list = results.loc[results["time_to_answer"].notna(), "time_to_answer"]
-        submitted_number = submitted_list.sum()/len(submitted_list))
+        submitted_number = submitted_list.sum()/len(submitted_list)
         assert (int(submitted_number)==int(correct_number)), ("The results don't look right. Please make sure that the part of the query "
                                                               "that calculates the values in the `time_to_answer` column is unmodified.")