The Lockers

Delphine and Théo
each have a locker.
Lockers
are numbered from 1 to 99.
The
two digits of Delphine’s locker number are the same as those
in Théo’s, but in reverse order.
If you
add the two
digits of Delphine’s locker number, the sum is exactly equal
to
the difference between Delphine’s and
Théo’s locker
numbers.
Question: What are
their locker numbers?