Explain why u would make one of the ascends a tens number when solving an addition problem

Can someone pls ! pls answer all. no explanation needed..

For what values of x is x2 + 2x = 24 true?

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