include hint around unique values when merging

Author: afeld

hw_2.ipynb

@@ -21,7 +21,7 @@
    "source": [
     "## Coding\n",
     "\n",
-    "The goal here is to practice [joining datasets through pandas](https://pandas.pydata.org/docs/user_guide/merging.html#database-style-dataframe-or-named-series-joining-merging). Hint: The instructions here are intentionally incomplete."
+    "The goal here is to practice [joining datasets through pandas](https://pandas.pydata.org/docs/user_guide/merging.html#merge). Hint: The instructions here are intentionally incomplete."
    ]
   },
   {
@@ -139,7 +139,7 @@
    "source": [
     "### Step 3\n",
     "\n",
-    "Use [`merge()`](https://pandas.pydata.org/docs/user_guide/merging.html#database-style-dataframe-or-named-series-joining-merging) to combine the two, and output the resulting table."
+    "Use [`merge()`](https://pandas.pydata.org/docs/user_guide/merging.html#merge) to combine the two, and output the resulting table."
    ]
   },
   {
@@ -173,12 +173,16 @@
     "\n",
     "<details>\n",
     "<summary><strong>Hint</strong></summary>\n",
-    "\n",
     "You're creating a \"number of [thing] per capita by borough\" table.\n",
     "\n",
     "1. Do a [`groupby()`](https://pandas.pydata.org/docs/user_guide/groupby.html) on the original dataset.\n",
     "1. Join with the populations by borough.\n",
     "1. Compute the per-capita values as a new column.\n",
+    "</details>\n",
+    "\n",
+    "<details>\n",
+    "<summary><strong>Hint 2</strong></summary>\n",
+    "Having trouble merging the datasets? Try looking at the unique values in the columns you're trying to merge on.\n",
     "</details>"
    ]
   },