Please help ill give brainliest its kinda confusing

4. find the geometric mean of 4 and 12. 24 8

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

Expresa commuter train leaves downtown sation and travels at a average speed of 55 miles per hour towards the north side sation, which is 50miles away. thirty minutes later, express commuter train #7 leaves north side and travels at a average speed of 35miles per hour towards downtown sation. at the moment the two trains pass each other, how far(in miles) is train #12 from the downtown sation and how long(in minutes) has the #12 train been traveling