Hello!
The answer is D.
Why?
From the statement we know that Pete can lay 15 more tiles per hour than Jim, so, it means that Pete's rate is equal to Jim rate plus 15 more tiles. We also know that both lays the same number of lays, so:
Then, since both lays the same number of lays at different times, Jim in 7 hours and Pete in 6 hours
So, since Petes lays 15 more tiles per hour than Jim:
Therefore, Jim's rate can be found using the equation D.
Have a nice day!