Question 549937
I'll do the first one to get you started


9x^3+x-2(8x^3-7x)



9x^3+x-2(8x^3)-2(-7x)



9x^3+x-16x^3+14x



-7x^3+15x



So 9x^3+x-2(8x^3-7x) = -7x^3+15x