$$30$$
Explanation
- Calculate the number of customers who choose Italian dressing by taking $$45\%$$ of $$200$$, which is $$200×45\% = 90$$
- Calculate the number of customers who choose vinaigrette dressing by taking $$30\%$$ of $$200$$, which is $$200×30\% = 60$$
- Find the difference between the number of customers who choose Italian dressing and vinaigrette dressing, which is $$90 – 60 = 30$$