A box could hold 32 staplers or 48 erasers. John placed 14 staplers in the box. How many more erasers could he place in the box?

wrong again.

He placed 14 staplers, not 14 erasers.
That is 14/32 = 7/16 of the capacity
So, that leaves room for 9/16 * 48 = 27 erasers

34 erasers