(2x^2+3x+4)(x^3+4x^2+3x)(x+4)
First use the distributive property for the first two:
(2x^5+8x^4+6x^3+3x^4+12x^3+9^2+4x^3+16x^2+12x)(x+4)
And then combine like terms:
(2x^5+11x^4+22x^3+25x^2+12x)(x+4)
Continue use the distributive property:
(2x^6+11x^5+22x^4+25x^3+12x^2+8x^5+44x^4+88x^3+100x^2+48x)
Continue combine like terms:
(2x^6+19x^5+66x^4+113x^3+112x^2+48x)
And that is your final answer.
Hope that help:)