Osborn the babysitter's latest job is with Nikita, a second-grader who requires a lot of homework help. Luckily, Osborn is very skilled at double-digit addition and subtraction. Early on, he offers Nikita help by reminding him of what to do step-by-step. For the middle problems, he sits back and offers Nikita helping questions only when the boy appears stumped. By the end, Osborn is offering no help at all.
Which strategy is Osborn using?