If every 5th customer gets a ticket and every 7th customer gets a sweater out of 400 customers how many get both?

The least common denominator of 5 and 7 is 35. With this stated, only multiples of 35 would receive both a ticket and a sweater. Therefore since 35 goes into 400 only 11 complete times with a remainder, only 11 customers would receive both the ticket and a sweater