-120x^8y^7
To simplify the expression, you can use the product rule of exponents, which states that when you multiply two terms with the same base, you add the exponents.
Here, we have:
-12x^5y^2y(10x^3y^4)
= -12 * 10 * x^5 * x^3 * y^2 * y^5 (using the product rule to simplify y^2 * y^4 to y^6)
= -120x^8y^7 (using the product rule to simplify x^5 * x^3 to x^8)
Therefore, the simplified expression is -120x^8y^7.