Answer:
The first answer. 8x^15 - 125y^3
Step-by-step explanation:
...because 8 is the cube of 2 and x^15 is the cube of x^5; also 125 is the cube of 5 and y^3 is the cube of y.
8x^15 - 125y^3 = (2x^5)^3 - (5y)^3
