There are 54 chips in a box. Each chip is either small or large. If the number of small chips is greater than the number of large chips by a prime number of chips, what is the least possible number of large chips?

B for number of big

S for number of small

S = B + a prime number

B+S=54

so

B+B+a prime = 54

2B + a prime = 54

2B is even

So can the prime be even or odd?

You can finish it.

A prime number can't be even. Oh wait. There is a single prime number that is even.