Answer:
1. -6y^4 +4y^2 -12
2. x - 19
Step-by-step explanation:
1.
(6y^4+3y^2-7) - (12y^4-y^2+5)
= -6y^4+ 4y^2- 12
2. 3(x-5) - (3x+4)
= (3x-15) - (3x+4)
= x-19
