I'll demonstrate number 1:
6-b=5b+30
+b +b (add b to both sides, so it cancels out the -b)
6=6b+30
-30 -30 (subtract 30 on each side)
-24=6b (now, divide each side by 6, to get b by itself)
-24/6=6b/6
-4=b
So the answer is b=-4. I hoped I helped you understand the concept a little more clearly. Good luck.