Answer
$=30x^{11}y^{12}$
Work Step by Step
When multiplying two exponential expressions, group factors with the same base: $$(-5x^{4}y)(-6x^{7}y^{11})$$
$$=(-5\times(-6))(x^{4}\times x^{7})(y\times y^{11})$$
$$=30x^{(4+7)}y^{(1+11)}$$
$$=30x^{11}y^{12}$$
