The speed of train a is 20 mph slower than the speed of train b. train a travels 230 miles in the same time it takes train b to travel 330 miles. find the speed of each train.

Recall your d = r*t  or distance = rate * time

so... let's say B is going at a speed of "r"
A is slower than B by 20mph, or whatever "r" is, A's speed is r - 20

at a certain time "t", A runs 230 miles whilst B runs 330 miles, same "t" time

so..  hmmm 

solve for "r", to see how fast B was going

what about A?  well,  A's speed is r - 20