Giving twenty points! (: (10 points each! )
if you can with this!
a is given, so you don't have to give me that one, you!

A. given
b. distributive property (a(b+c)=ab+ac)
c. addition or commutative property (a+b=b+a)
d. subtraction property of equality (if a=b, then a-c=b-c)
e. division property of equality (if a=b, then a/c=b/c)
f. equality property (if a=b, then b=a)

A. is distribution  property where you just multiply 3(n+4)= 3n+12
b. combine like terms 3n+3n=6n
c.subtract 42-12=30
d.divide 30 by 6n
e. you answer 5=n
f. They just turn it around because n has to be in the front

hope it is what you are looking for