Which expression is equivalent to X^-1Y^4 / 3x^-5y^-1

Whenever you have negative exponents over a variable, what you want to do is move that variable to the other side of the fraction and make the exponent positive. For this expression, the first step would therefore become x^5y^5 / 3x. (Exponents with the same coefficient are added together to get y^5.) Then, when you have like coefficients in the numerator and the denominator, you subtract those exponents. Your final answer is therefore x^4y^5 / 3.