How many more pupils attended school in Ghana in 1920 compared to 1890?
return Ghana ;return pupils attended school of #1 ;return #2 in  1920 ;return #2 in  1890 ;return number of  #3 ;return number of  #4 ;return the  difference of #5 and  #6
['select', 'project', 'filter', 'filter', 'aggregate', 'aggregate', 'arithmetic']