Need help with number 8 and 9

Suppose there are 10 five and six-year-old attending a birthday party. when a 30 year old mother walks into the room with an infant in her arms, what happens to the mean age in the room? what happens to the standard deviation of ages in the room? a. the mean and standard deviation of both change. b. the meaning will change, but the standard deviation will stay approximately the same. c. i mean will stay approximately the same, but the standard deviation will change. d. the mean and standard deviation will both stay approximately the same.

Jayne is studying urban planning and finds that her town is decreasing in population by 3% each year. the population of her town is changing by a constant rate. true or false?

If i purchase a product for $79.99 and two accessories for 9.99 and 7.00 how much will i owe after taxes applies 8.75%