Help me please on this problem

Help me please on this problem class=

Verified Answer :

1st=m
2nd=m-1200
3rd=(m-1200)*1.3
3rd=1.3m-1560
(m+m-1200+1.3m-1560)/3
(3.3m-1200-1560)/3
(3.3m-2760)/3
1.1m-920 is the average number of visitors.

Hope this helps :)