diff --git a/lib/koans/05_functions.ex b/lib/koans/05_functions.ex
index c791938..e4a3b78 100644
--- a/lib/koans/05_functions.ex
+++ b/lib/koans/05_functions.ex
@@ -52,7 +52,7 @@ defmodule Functions do
   end
 
   def sum_up(thing) when is_list(thing), do: :entire_list
-  def sum_up(thing), do: :single_thing
+  def sum_up(_thing), do: :single_thing
   koan "You can 'guard' functions against their arguments" do
     assert sum_up([1,2,3]) == :entire_list
     assert sum_up(1) == :single_thing
diff --git a/lib/koans/07_arithmetic.ex b/lib/koans/07_arithmetic.ex
index b7d37d3..f64e164 100644
--- a/lib/koans/07_arithmetic.ex
+++ b/lib/koans/07_arithmetic.ex
@@ -51,12 +51,4 @@ defmodule Arithmetic do
   koan "it finds the minimum in a list" do
     assert Enum.min([1,2,3,4]) == 1
   end
-
-  koan "it can not divide by zero" do
-    try do
-      1 / 0.0
-    rescue
-       ArithmeticError -> true
-    end
-  end
 end
diff --git a/lib/koans/08_structs.ex b/lib/koans/08_structs.ex
index 8e70a12..569e260 100644
--- a/lib/koans/08_structs.ex
+++ b/lib/koans/08_structs.ex
@@ -6,7 +6,8 @@ defmodule Structs do
   end
 
   koan "structs are defined and named after a module" do
-    assert %Person{}
+    person = %Person{}
+    assert person == %Person{}
   end
 
   koan "you can access the fields of a struct" do
@@ -53,7 +54,6 @@ defmodule Structs do
   koan "are basically maps" do
     silvia = %Person{age: 22, name: "Silvia"}
 
-    assert is_map(silvia)
     assert Map.fetch!(silvia, :age) == 22
   end
 end