hi, could someone check the answers of these for me? btw, the book says that they are all wrong. i dont understand why.

1. If z = 2 + i, evaluate:

a) 3z = 6 + 3i

b)

2. Solve for z; expressing answers in the form a + ib

a)

b) Totally clueless about this one:

Solve for x.

3. Simplify:

I got 3i/2. but the answer is -3i/2. I dont get why.

Thanks