Yo pls help me out, the question is on the picture. ill mark brainliest if its correct. NO LINKS!

Determine whether the set of whole numbers is closed under addition. explain why the set is or is not closed. give an example.

The parabola y = x² - 4 opens: a.) up b.) down c.) right d.) left

With this question substitute t=3 and t=5 to determine if the two expressions are equivalent. 4(t + 3) 4t+12 which statements are true? check all that apply. a. the value of both expressions when t =5 is 32. b. the two expressions are not equivalent. c. the value of both expressions when t=3 is 15. d. the value of both expressions when t=5 is 23. e. the two expressions are equivalent. f. the value of both expressions when t=3 is 24.