diff --git a/src/ii_collections/n21Partition.kt b/src/ii_collections/n21Partition.kt
index f95b0da35..e53e8b896 100644
--- a/src/ii_collections/n21Partition.kt
+++ b/src/ii_collections/n21Partition.kt
@@ -11,6 +11,9 @@ fun example8() {
 }
 
 fun Shop.getCustomersWithMoreUndeliveredOrdersThanDelivered(): Set<Customer> {
-    // Return customers who have more undelivered orders than delivered
-    todoCollectionTask()
+    return customers.filter {
+        val (delivered, undelivered) = it.orders.partition { it.isDelivered }
+
+        undelivered.size > delivered.size
+    }.toSet()
 }