The value of n in the proportion is 16. The answer is 16 because to find the difference you first take 28 and divide it by 7 which gives you 4. To check and make sure that 4 is right you would multiply 7 by 4 which gives you 28. You then would take 4 and multiply it by 4 since that is the difference. 4 times 4 gives you your answer of 16.