reinout-g

the inverse sin is also indicated as 

$$sin^{-1}(x)$$

$$arcsin(x)$$

$$asin(x)$$

On the web2.0calc.com calculator you can find it by using 2nd -> asin

Alright so first let's look at what we have.

First work away the brackets, for example;

$$3(x-4) = 6(2x+1) \Rightarrow 3x-12 = 12x+6$$

Now substract $$12x$$ from both sides

$$-9x-12 = 6$$

Add $$12$$ to both sides

$$-9x = 18$$

Divide both sides by -9

$$x = -2$$

voila! 

This is the best I can do for you

Wolfram is now building a timemachine so they can ask einstein about question c.

Reinout

I knew it could be done in that way.

I just preferred the longer route.

I giveth thee this glowing composition to be guideth to CPhill by thy most excelling rider.

Jupiter be curseth for not granting me the passage to him myself.

If thou triumphstedth I reward thee by not giving thy lands the curse of lightning.

You can find the answer by adding all the values and dividing by the number of values (in this case 4)

So the answer is

$${\frac{\left({\mathtt{4.5}}{\mathtt{\,\small\textbf+\,}}{\mathtt{3.5}}{\mathtt{\,\small\textbf+\,}}{\mathtt{5.5}}{\mathtt{\,\small\textbf+\,}}{\mathtt{2.9}}\right)}{{\mathtt{4}}}} = {\frac{{\mathtt{41}}}{{\mathtt{10}}}} = {\mathtt{4.1}}$$

So your answer is $4.10

Reinout 

You don't want your answer now?

then I'll give it later...

I think you meant 40% and 60%.

That would make sense.

Then the first answer is correct.