Iborrow £50 off my mum £50 off my dad and buy a jumper for £97. £3 is left so i give £1 to my mum £1 to my dad and i kept £1 which i now owe £49 to my mum and dad so how comes that only adds up to £99

Step-by-step explanation:

first we used the $3 in change to inaccurately subtract $1 from what you owe each of your parents ($50 - $1 = $49) (you're counting backwards!),

and then added to that total debt balance of  $98 ($49 I owe mom + $49 I owe dad) the $1 which you kept for yourself to then arrive at the false sum of $99

we should have correctly and consistently added the $3 change back onto the $97-cost of the shirt so that the correct total balance of $100 would then be realized and accounted for as follows:

BEFORE THE PURCHASE OF THE SHIRT

Amount borrowed from mom -- $50

Amount borrowed from dad   --  $50

Total borrowed                          --  $100

AFTER THE PURCHASE OF THE SHIRT

Cost of shirt                              --     $ 97

plus $ 3 change:

One dollar to mom                  --     $   1

One dollar to dad                     --     $   1

One dollar for myself              --      $  1

Total                                         ---     $100

boxplot e is the answer