What are the 2 steps that are wrong

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

The suare root of 9x plus 7 plus the square rot of 2x equall to 7

Find the least common denominator for thesetvo rational expressions.n^2/n^2+4n+4 -3/n^2+7n+10