I believe the first and last one are polynomials. Usually they start with the highest exponent first and then work their way down.
The top left is the correct answer, because the sides are parallel.
Hope this helps!
686 barrels left. If I'm not mistaken this should just be simple subtraction
The coefficient of y∧15×∧2 in expansion of (y∧3+x)∧7 is (15×2)+(3×7)= 51