Pls me asap for 7, 8, and 9. a and b (show work for + lots of points

Statement: if two distinct planes intersect, then their intersection is a line. which geometry term does the statement represent? defined term postulate theorem undefined term

Solve for x -2.3(r - 1.2 ) = -9.66 enter you answer as decimal.

How many different three-digit numbers can be formed using the digits 1 comma 2 comma 9 comma 6 comma 4 comma 3 comma and 8 without repetition? for example, 664 is not allowed.