If the sum of an A. P is 21. if the 3rd term - 1st term = 4. find the sum of the next four terms.​

What is the result of the greenhouse effect? a. heat is deflected from the atmosphere. b. heat is released from the atmosphere. c. heat is kept in the atmosphere. d. plants are able to grow in the tropics where the air is the heaviest.

How many time zone are there on earth

What could the united states of america do to improve their status? name at least 3(ap human geography)