At 52 km/h, its kinetic energy is Joules. The work done by the brakes is the difference between those two: Joules.
(Notice the order of those speeds. The truck slows down so the work done is negative.)
The truck decelerates at so its acceleration is . Force equals mass times acceleration (that formula isn't given here but I am sure you know it): .
Now use W= Fd: .
The unknown mass, m, cancels and you can solve for d.