 <translate> There were 80 / 2 = 40 wireless mice sold. There were 80 / 4 = 20 optical mice sold. So, there were a total of 40 + 20 = 60 wireless and optical mice sold. Therefore, 80 - 60 = 20 trackball mice were sold this month. So the answer is 20. <yor> 80 / 2 = ogójì òṣùwọ̀n òṣùwọ̀n òṣùwọ̀n tí a tà. 80 / 4 = ogún òpó tí wọ́n tà. Nítorí náà, àpapọ̀ 40 + 20 = 60 alágbèéká àti àwo tí a fi ojú rí ni a tà. Nítorí náà, 80 - 60 = ogún eku trackball ni a tà ní oṣù yìí. Nítorí náà ìdáhùn náà ni 20. 