Add exercises that were initially left out

thinkcspy/Chapter-16-Exercises/Problem5_fibonacci.py

@@ -0,0 +1,14 @@
+# Runestone.Academy thinkcspy course
+# Chapter 16
+# Problem 5
+
+def fibonacci(number):
+    if number < 0:
+        return
+    elif number == 0 or number == 1:
+        return number
+    else:
+        number = fibonacci(number - 1) + fibonacci(number - 2)
+        return number
+    
+print(fibonacci(10))