hi i would be very grateful if anyone could help me out with any of the questions

(a) use the definition of addition for rational numbers to verify that it satisfies the commutative and associative laws.

(b)use the definition of mutiplication for complex numbers to verify that it satisfies the commutative and associative laws.

(c)solve the system of linear equations in complex numbers:

(2 + i)x + (-3i)y = 3 + i

3ix + (3 - 2i)y = 3 - 3i

(d)how many complex numbers z are there that z^6=1? Calculate them and sketch the argand diagram.

what i have done so far

(a)

well i got this for the definition of addition for rational numbers but i need help for the second part it seems simple yet i cannot manage to do it.

(b)Multiplication:

(c) i've been taught how to solve systems in geometry but i cannot solve this.

(d)z=1^(1/6)

z=1

1(cos(theta)+isin(theta)) i don't know how to figure out the angle of theta

if anyone could help with any part i would appreciate it alot