How many more abortions were done by medical abortion compared to those classified by instillation abortion?
return abortions ;return #1 that were done by medical abortion  ;return #1 that were classified by instillation abortion  ;return number of  #2 ;return number of  #3 ;return difference of #4 and  #5
['select', 'filter', 'filter', 'aggregate', 'aggregate', 'arithmetic']