To ride to school, elaine takes 7 minutes to ride 18 blocks. what is her unit rate? assuming she rides at a constant speed, how long should it take her to go 50 blocks?

Can someone me and do the problem plz so i can understand it more better

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 to find the exponential function y=ca^x, with points (1,2) and (2,1)