Can you explain to me how i would solve this problem? can you explain/and show all the steps? also, is there anyway i can check my answer to see if it is correct? if so, explain to me? 22 = z + (-9)

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

Which of the following contains a variable?

Using elimination, what is -4x+2y=-12 4x+8y=-24