Hi there!
To write the polynomials in standard form, we need to put the variables that has the highest exponent in front.
As you can see we have y^15 so it should be in front and so on...
Thus, the answer is
y^15 - y^12 + y^10 - 4y
I hope this helps and please let me know if you have questions about the answer.
Good luck with your study!