The answer is 81. doficjanansoaosj
A readymade cube or a cube that you can make with paper and wood sticks?
For the numeric part, you'll have to find the GCD of 15 and 25, which is 5. So, we can factor a 5 and we have

As for the literal part, you can factor
because it's the power of s with the smallest denominator. So, we have

Your answer is 7g^4
Hope this helps!