SUBTRACTION WITH BORROWING
   Start with the right-hand column as usual.
                            63  -
                            27
 When you try to take the 7 away from the 3, 
                     you can't.
  If you have 3 pence and a friend wants you 
         to lend her 7 pence, you can't.
                           
                         TU
                         63  -
                         27
      Look at the number 63.
      It’s made up of 6 tens (60) plus 3 
      units (3).
                           
                         63  -
                         27
      You borrow one of the tens off the 
      60, and lend it to the 3 to make it 
      13.
      This leaves you with 5 tens (50) 
      plus 13 - which still makes 63!
                           
      To show you have borrowed 10 off 
      the 60, cross off the 6 and make it 
      into a 5.
      Put a 1 in front of the 3 to make it 
      into 13.
      The sum now looks like this:
                       5
                       6  13  -
                       2    7
                             
         Take the 7 away from the 13.
                             5
                             6  13  -
                             2    7
                                   6