minta tolong no 15 yaa makasih

12. 5x^2y-3xy^2+6x^2y
=(5x^2y+6x^2y)-3xy^2
=11x^2y-3xy^2

13. 3a-5b-a-4b
=(3a-a)-(5b-4b)
=2a-b

14. 5a^3 × 6a^2b + 10a^4
=(5a^3 × 6a^2b) + 10a^4
=30a^5b + 10a^4

15. (-15c^6d^3) : 3c^4 × 7e^2
= (-5c^2d^3) × 7e^2
= -35c^2d^3e^2

Maaf kalau salah.
Semoga bermanfaat.