Please help me! I really need help!

1. What is the simplified form of the following expression?

6m2 + 7.2n -4n + 2.5m2 -n

2. Simplify the following expression

1/2(22m+30)

3. Which sum or difference is equivalent to the following expression

3x+2/6


4. What is the simplified form of the following expression?

-(3y - 9z)