 
 <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. <ibo> E nwere 80 / 2 = 40 wireless òké rere. E nwere 80 / 4 = 20 optical òké rere. Ya mere, e nwere ngụkọta nke 40 + 20 = 60 wireless na ngwa anya òké rere. N'ihi ya, e rere 80 - 60 = 20 trackball mice n'ọnwa a. Ya mere azịza ya bụ 20. 