Let's try 4+3=7. Yes, that equals 7, but is it the maximum possible product? Let's try 14-7=7. That equals 7 and it is a bigger maximum possible product, but is it the biggest? No.
Let's try 100-93=7. Yup, that works!
So, that means that 100-93=7 should be the answer. Hope this helps you:)