Algebra I, Literal Equation help

So I need help on literal equations... We just started today, and I went to do my homework, but I can't do it if I don't understand it.

I understand the ones like this;
7t + x, for t
t = x/7

r = wp, for p
p =r/w

However, the ones where what you're solving for is on both sides I don't get, such as;

4m - t = m, for m

7a - b = 15a, for a

-5c + d = 2c, for c

And so on. I'm not looking for just the answers, I'd like to know how I solve them.

you need to combine like terms where possible.. I'll use the last problem as an example

-5c + d = 2c

+5c added to both sides

d = 7c -----> solve for c ------> c = d/7