Keith exercises x hours a week. troy exercises three hours less than keith and joe exercises two times more than troy. which expression represents the amount of time joe exercises?

If Keith is represented by x, and Joe is three less than Keith, Troy is represented by x-3. 
Then, we know that Joe exercises for twice the amount of time as Troy, we multiply the expression for Joe by two. 

Keith = x
Troy = x-3
Joe = 2(x-3)