One day a store sold 21 sweatshirts. White ones cost 11.95 and yellow ones cost 13.50. In all, 277.30 worth of sweatshirts were sold. How many of each color were sold

Aresearch study is done to find the average age of all u.s. factory workers. the researchers asked every factory worker in ohio what their birth year is. this research is an example of a census survey convenience sample simple random sample