Sale of items in May = 16% of 7500 = 1200
Sale of items in June = 24% of 7500 = 1800
Sale of items in July = 28% of 7500 = 2100
Sale of items in August = 32% of 7500 = 2400
Sale of balls in May = 60% of 1200 = 720
Sale of balls in June = 55% of 1800 = 990
Sale of balls in July = 75% of 2100 = 1575
Sale of balls in August = 40% of 2400 = 960
Then, sale of bats in May = 1200  -  720 = 480
Sale of bats in June = 1800  -  990 = 810
Sale of bats in July = 2100  -  1575 = 525
Sale of bats in August = 2400  -  960 = 1440
In tabular form:
| Month | Sale of items | 
| Total | Balls | Bats | 
| May | 1200 | 720 | 480 | 
| June | 1800 | 990 | 810 | 
| July | 2100 | 1575 | 525 | 
| August | 2400 | 960 | 1440 | 
Sale of bats in September = 3 * 760  -  525  -  1440 = 315