30 girls and boys have planned for a picnic. there is a ratio of 3 girls to 7 boys. how many boys are there?

If 10 men take 18 days to mow 60 acres of grass, how long will 15 men take to mow 80 acres?

Twelve less than a number is at most 20

The management of a supermarket wants to adopt a new promotional policy of giving a free gift to every customer who spends more than a certain amount per visit at this supermarket. the expectation of the management is that after this promotional policy is advertised, the expenditures for all customers at this supermarket will be normally distributed with a mean of $95 and a standard deviation of $20. if the management wants to give free gifts to at most 10% of the customers, what should the amount be above which a customer would receive a free gift?