(-3m²n³)² (-2m³n) ³(1/72m²n³)

Use PP -3m²n³ must be multiplied 2 times and -2m³n must be multiplied 3 times, but 1/72m²n³ does need to (Because there is no exponent, and that is same as that there is 1).

(9m⁴n⁶) (-8m⁹n³)(1/72m²n³)

It can be multiplied with same bases.

-72m¹³n⁹/72m²n³

And it can be divided

-m^13-2n^9-3= -m¹¹n⁶

We can get the results that a is -1, b is 11, and c is 6, so -1+11+6 is equal to 16

We learned about what is prime factorization.

It consists of prime factors. We can use them when we should find the prime factors. First of all, it should be divided by the smallest prime number, the number (72 is an example for this explanation) should keep dividing by the smallest prime numbers. Lastly, gather all of the prime numbers if it becomes the prime number, and make a prime factorization.