Simplify the following expressions

1. (-4a-12b+8c)÷(-4)
= -4a/-4 - 12b/-4 + 8c/-4
= a + 3b - 2c

2. (15m^3 - 5m^2 - 10m) ÷ (-5m)
= 15m^3/-5m - 5m^2/-5m - 10m/-5m
= -3m^2 + m + 2

3. 12y^3 -12y^2 +6y
　－－－－－－－－
　　　-3y
= 12y^3/-3y - 12y^2/-3y +6y/-3y
=-4y^2 + 4y - 2

4. 16a^3b-36ab^3
　－－－－－－－
　　　 4ab
= 16a^3b/4ab - 36ab^3/4ab
= 4a^2 - 9b^2