Essentially, the way to do the first three questions, is to:
1. Multiply all the denominators out. (numbers, or non-letters, can be left in the denominator)
2. Multiply out all the brackets.
3. Collect like terms.
When solving, we add a few more steps:
4. Collect what you're solving for to one side of the equation. Remove everything else to the other side.
5. Factorise what you want out.
6. Divide by what's left.
1.
\sqrt{x-1}}{x-1})
2.
(x+1)}{x-1}-\frac{(x-1)(x+1)}{x+1}+(x-1)(x+1)<br />\\ =x+1-x-1+x^2-1<br />\\ =x^2-1)
3.
=sf<br />\\ r=\frac{sf}{s-f})
4. For this question, the "n" you're talking about is, presumably, this symbol:

. This is referred to as an intersection. An intersection just takes what's in common - for example,

. Reckon you can give this one a shot, now?
5. Apply the remainder theorem. If f(x)/(ax-b) has remainder r, then f(b/a)=r. Use this to set up a new quadratic equation, which should help you solve for your a.
6. This one's a bit trickier - one way is to work off the graph, here's another:
>\log_8(2050)<br />\\ n\log_8(8)>\log_8(2050)<br />\\ n>\log_8(2050))