What does a closed circle on a number line mean?

Element x decays radioactively with a half life of 8 minutes. if there are 450 grams of element x, how long, to the nearest tenth of a minute, would it take the element to decay to 37 grams?

At a local museum, the total price for one adult and one child is $11. mrs. smith paid for herself and her three children. she spent $19. record the system of equations to be solved and then find the price of an adult and child ticket using either elimination or substitution.

Awoman who is 64 inches with a shoulder width of 16 inches. write an equation relating the height h to the width w. find the height of a woman who has ashoulder width of 18.5 inches