Exponents

how do I multiply exponents? (x-2y-4)-3(y4y3) the numbers are exponents

This is how you could have written it      (x^-2y^-4)^-3(y^4y^3)

$(x^{-2}y^{-4})^{-3}\times (y^4y^3)\\ =(x^{-2*-3}y^{-4*-3})\times (y^{4+3})\\ = (x^{6}y^{12})\times (y^{7})\\ = x^{6}y^{12}y^{7}\\ = x^{6}y^{12+7}\\ = x^{6}y^{19}\\ $