Răspuns :
30-6-6-6-6-6=0 inseamna ca 30:6=5 pentru ca l am scazut pe 6 de 5 ori.
21-7-7-7=0 deci 21:7=3
36-6-6-6-6-6-6=0 deci 36:6=6
49-7-7-7-7-7-7-7=0 deci 49:7=7
60-6-6-6-6-6-6-6-6-6-6=0 deci 60:6=10
70-7-7-7-7-7-7-7-7-7-7=0 deci 70:7=0