-4(x^4+2y^3)
here's how you solve it!
collect the like terms
19x^4-16x^4-8y^3-7x^4
Once you collect the like terms you are left with
-4^4-8y^3
Then you factor out the -4 from the problem
-4(x^4+2y^3)
Then you are left with the answer:
-4(x^4+2y^3)
Hope this helps! :3