Remove .md and image files and move python files into main chapter folders

thinkcspy/Chapter-9-Exercises/Problem12.py

@@ -0,0 +1,23 @@
+# Runestone.Academy thinkcspy course
+# Chapter 9
+# Problem 12
+
+def remove_all(substr,theStr):
+    # your code here
+    pos1 = 0
+    pos2 = len(substr)
+    newStr = theStr
+    
+    while pos1 < len(newStr):
+        currentPos = newStr[pos1:pos2]
+        
+        if substr == currentPos:
+            newStr = newStr[:pos1] + newStr[pos2:]
+        else:
+            pos1 += 1
+            pos2 += 1
+       
+    return newStr
+
+
+print(remove_all("e", "treeeleee"))