Bethany was born in minnesota, but now she lives in illinois, close to where
illinois, wisconsin, and lowa meet. she works in wisconsin, but she buys all
of her clothes at a store in lowa. if the sales tax rates for the four states are
as shown in the following table, which sales tax rate does bethany pay on the
clothes she buys?

Let a be the smaller of the two primes.

Now the middle of 2 primes is always even. So the middle number a+1 is divisible by 2.

Next the smaller of the primes when divided by 3 can have remainders 1,2.

1 is ruled out as possible remainder because then the remainder of a+2, the bigger of the primes would be (a+2) mod 3=(1+2) mod 3=3 mod 3=0,a contradiction since a prime number(except 3) when divided by 3 cannot have 0 as remainder.

So 2 is the only possible remainder of a. So the remainder of the bigger of the two primes when divided by 3 is (a+2) mod 3= (2+2) mod 3=4 mod 3=1.

This implies the middle number must have remainder (a+1)mod 3=(2+1)mod 3=3 mod 3=0. So the middle number is divisible by 3 also.

Hence a+1 is divisible by both 3 and 2 and since 2 and 3 have no common factors, so the middle number is divisible by 6