Final answer:
To simplify the expression -3x^-5y^4^3, we can convert the negative exponents to positive exponents by taking the reciprocal.
Step-by-step explanation:
To simplify the expression -3x^-5y^4^3 using positive exponents, we need to convert the negative exponents to positive exponents. When we have a negative exponent, it can be written as the reciprocal of the positive exponent. So, -3x^-5y^4^3 can be written as -3/y^12x^5. The answer is option C. -27x^-5y^12.