what is the solution set for l2x-5l= 7 for x?

Well, you know what the |.. | means?

It means that anything inside it must be taken as positive, so |3| = 3, |-3| = 3

so you are looking for the 2 solutions:

2x-5 = 7

and

2x-5 = -7

now you can find both solutions.