What is the product of (9+x)(9-x)

Which ordered pair (c, d) is a solution to the given system of linear equations- c+2d=13 -9c-4d=-15

Ineed with math stuff it involves graphs

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.