Update formative-assessment.md

Fix trick question link by switching to reference link

Author: ndporter

episodes/formative-assessment.md

@@ -178,7 +178,7 @@ Share the major points of your discussion in the collaborative notes document.
 
 The Trainers will assign your group a type of exercise to focus on.
 Read about your given exercise type on the indicated pages of
- [_Is This a Trick Question?_][trick-question]:
+ [_Is This a Trick Question?_][trick-question-ref]:
 
 - multiple choice (page 13)
 - true-false (pages 20 & 21)
@@ -208,7 +208,7 @@ Trainers will lead a discussion about your findings for your chosen exercise typ
 
 ### Recommended Reading
 
-Both of the resources linked from the exercise above, [the _Exercise Types_ chapter of _Teaching Tech Together_][ttt-exercises] and [_Is This a Trick Question?_][trick-question] ([ref][trick-question-ref]) are worth reading in full. They collect a lot of insightful discussion and illustrative examples, which can prove very useful when designing exercises for your lesson.
+Both of the resources linked from the exercise above, [the _Exercise Types_ chapter of _Teaching Tech Together_][ttt-exercises] and [_Is This a Trick Question?_][trick-question-ref] are worth reading in full. They collect a lot of insightful discussion and illustrative examples, which can prove very useful when designing exercises for your lesson.
 
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