Description: Add and subtract negative fractions with unlike denominators. Created by Sal Khan. But it immediately jumps out at me that these last two numbers have a 6 in the denominator. I'm going to view this as negative 7/6 minus 3/6. So if we have negative 7/6 minus 3/6, that's going to be the same thing as negative 7 minus 3 over 6.*Teacher Advisor is 100% free.