Which of the following statements are true? select all that apply.
1. for all real numbers a and b, a+b=b+a
2. for all real numbers a and b, ab=ba
3. for all real numbers a and b, a-b=b-a
4. for all real numbers a, b and c, (a+b) + c = a + (b+c)
5. for all real numbers a, b and c, (a-b) - c = a - (b-c)
6. for all real numbers a, b and c, a(b+c)= ab+ac

According to a study conducted in 2015, 18% of shoppers said that they prefer to buy generic instead of name-brand products. suppose that in a recent sample of 1500 shoppers, 315 stated that they prefer to buy generic instead of name-brand products. at a 5% significance level, can you conclude that the proportion of all shoppers who currently prefer to buy generic instead of name-brand products is higher than .18? use both the p-value and the critical-value approaches.