Ok.. Math problems. Algebra 2

So.. basically im being homeschooled online, and i have been teaching myself due to the fact that my parents are both full time teachers, and i am also a part time English/Chinese tutor. (This all to explain myself.)
Anyway, I cannot for the life of me understand math. It's like a foreign language to me (oh the irony.)

If one of you could help me with it, that'd be amazing.

P=2L+2W ; solve for L

C=2 pi r; solve for r

P= 3r+2s; solve for s

A=1+prt; solve for r

C= 5(F-32)/ 9 ; solve for F

A= h/2(a+b); solve for h



Ok.. so basically what im looking for is how to solve it. You don't have to solve them all, i just desperately want to understand this stuff.
Thank you so much<3

1. P= 2L +2W
from the right hand side, we can see that 2 is common to both L and W, therefore, we'll bring it out like this:
P=2(L+W)
if this parenthesis are solved for, we'll get back to the original equation. Now didvide both side by 2 to get:
P/2=2(L+W)/2
on the right hand side (RHS), 2 will cancel out one another to get:
P/2=L+W
now, if W moves to the other side (Left), by crossing over the = sign, it changes it sign from + to -. As in:
(P/2)-W=L . Therefore,
L= (P/2)-W. Solved

2. C=2pi r
all we need to do here is to find a way to let r be alone and that is by dividing both sides by 2pi:
C/2pi= 2pi r/2pi
where 2pi will cancel one another on the RHS to get
C/2pi= r. Therefore,
r= C/2pi. Solved.

3. P=3r+2s.
All we need to do is to find a way of making s be alone on one side and the rest on the other side. First step is by making 3r cross to the other side and this will change its sign form + to -. As in:
P-3r=2s
s is not alone yet, to finalize this, we'll have to divide both sides by 2:
(P-3r)/2=2s/2
with 2cancelling 2 on the RHS, we'll be left with:
(P-3r)/2=s. Therefore,