Marcia has 412 flowers for centerpieces. she uses 8 flowers for each centerpiece. how many centerpieces can she make?
(this is interpreting the remainder)

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

How do you determine if an ordered pair is a solution to a given equation?

I’m really confused and need to learn this