How many more non-gang robberies were there compared to kidnappings and arson cases combined?
return non-gang robberies ;return kidnappings ;return arson cases ;return number of  #1 ;return number of  #2 ;return number of  #3 ;return sum of #5 and  #6 ;return the  difference of #4 and  #7
['select', 'select', 'select', 'aggregate', 'aggregate', 'aggregate', 'arithmetic', 'arithmetic']