I'm assuming your trying to find how much pizza he has left.
You need to subtract the two fractions because the denominators are already the same.
When subtracting fractions, you leave the denominator and regularly subtract the numerator.
Your answer will be 2/8 which equals 1/4th
15-6x2=X im not sure if thats right but its what i got
The answer to this question is D. or C.