title: How to get same key with value in 2 different tuples
body: <p>dept_id = [(121, 20000), (121, 30000), (122, 20000), (123, 40000)]</p>
  
  <p>121 - is ID
  20000 -  is salary
  Now I want to print</p>
  
  <p>Average of each dept from above</p>