feat: add substract with image reference

ENDPOINTS-EXAMPLE.md

@@ -4,6 +4,24 @@ Test quick examples for each endpoint:
 
 ## Grade 1
 
+### Subtract with image reference
+
+```bash
+curl -X POST "http://127.0.0.1:8000/math/grade_1/subtract_with_image_reference" \
+  -H "Content-Type: application/json" \
+  -d '{
+    "object_name": "peces",
+    "initial_quantity": 5,
+    "removed_quantity": 2,
+    "actor_name": "Diego",
+    "figure": {
+      "id": "fish",
+      "name": "Fish",
+      "image_path": "/images/fish.png"
+    }
+  }'
+```
+
 ### Join corresponding sums
 
 ```bash