Answer: Jim can lay 25 tiles per hour.
Explanation:
Let be "x" Jim's rate and "y" Pete's rate.
We know that Jim completed half the floor in 4 hours, then:

And Pete completed the other half of the floor in 2 hours, then:

Since Jim completed half the floor and Pete completed the other half:
[Equation 1]
We also know that Pete can lay 25 more tiles per hour than Jim, then:
[Equation 2]
Then, we can substitute Equation 2 into Equation 1 and solve for "x":

Therefore, Jim can lay 25 tiles per hour.