This is a very tricky question.
So take
A: 3^8 - 3^7 and B: 3^7.
A: 3^8 and B: 3^7 + 3^7
A: 3 x (3^7) and B: 2 x (3^7)
You can cancel out the 3^7 from both sides. This leaves you
A: 3 and B: 2
A: 3 > B: 2
So A.
Note: 3^7 means 3 raised to the power of 7. 3^8 means 3 raised to the power 8.
Quantity A if simplified = 3^7( 3 - 1 )
Quantity B will remain 3^7
Lets divide 3^7 from both sides
Quantity A = 2 while Quantity B = 1
Hence, A > B .
You can try with something smaller to if you’d like instead of 3^8 take 3^3 and then calculate it
ex: 3^3 - 3^2 vs 3^2
27-9 = 18 while Quantity B = 9
Hence A > B