I think I’m right but I would like someone to look over it

Simplify a7/a4 a) 1/a3 b)-a/a2 c)a4/a3 d)a3

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

Write as a product: ac^2–ad+c^3–cd–bc^2+bd