diff --git a/book/numerical_methods/6-initial-value-problem-singlestep.ipynb b/book/numerical_methods/6-initial-value-problem-singlestep.ipynb
index 3e8fd62ba414a63c1f7053f77ff3e794b0a23e78..2100d12797088647d054647eded02dc0bf8486e7 100644
--- a/book/numerical_methods/6-initial-value-problem-singlestep.ipynb
+++ b/book/numerical_methods/6-initial-value-problem-singlestep.ipynb
@@ -533,7 +533,8 @@
     ":::{card} Exercise:\n",
     "\n",
     "Modify the step size in the Implicit Euler code, try to make the solution unstable. What do you notice?\n",
-    "```"
+    "\n",
+    ":::"
    ]
   },
   {
@@ -686,7 +687,7 @@
    "id": "560fbf20",
    "metadata": {},
    "source": [
-    ":::{card}\n",
+    ":::{card} Exercise\n",
     "\n",
     "Use the forward Euler to approximate the solution to the initial-value problem.\n",
     "\n",