tolong ya,pakai cara

100 % = 360°
pulpen = 90° = 90/360 = 1/4 = 0,25 = 25 %
pensil = 100% - ( 25%+40%+15%)
             = 100% - 80%
              = 20 %
25 % = 20 lusin
20 % =   20 /25 * 20  = 16 

jadi banyaknya penjualan pensil = 16 lusin
jawab.c.16 lusin

semoga membantu yaa