feat: examples

ex/theme-03-numbers-0-12/practice-04.md

@@ -2,6 +2,8 @@
 
 ### Exercise 10. Complete the word
 
+Example: r e _ -> red
+
 1. f _ v e
 2. s e v _ n
 3. e i g h _
@@ -9,6 +11,8 @@
 
 ### Exercise 11. Write the number figure
 
+Example: three -> 3
+
 1. three -> __________
 2. seven -> __________
 3. ten -> __________
@@ -16,6 +20,8 @@
 
 ### Exercise 12. Answer with a number word
 
+Example: How many apples? 🍎🍎 -> two
+
 1. How many ducks? 🦆🦆🦆  __________
 2. How many flowers? 🌷🌷  __________
 3. How many cups? ☕☕☕☕☕  __________