ln of what?       

y= I suppose?       

It also needs brackets because I know what is on the bottom of the fraction.  

$$2-\sqrt{13}$$

That is as simple as it gets.

y=A*sin[B(x+C)] +D

NOTE: the B is outside the bracket

A=amplitude

period is 2pi/B

Phase shift is -C

vertical shift is D

Yes you have your clever moments very often.   

It was cluey for you to notice that Chris.     

Complementary angles are angles that add up to 90.

Complementary trig ratios are ones where the values are equal for complementary angles.

I am probably not wording that very well.

Cosine stands for complementary ratio of sine   (at least that is how I think of it)

     Cosine(theta)=sine(90-theta)

Cotangent stands for complementary ratio of tan

     Cot(theta)=tan(90-theta)

Cosec stands for complementary ratio of sec

     cosec(theta)=sec(90-theta)

If you remember this it can help a lot.    

y=cx

substituting you get

$$\\11=c\times 18\\\\
c=\frac{11}{18}\\\\
y=\frac{11}{18}\times x$$

Now just substitute in different values of x to get the corresponding values of y  

Feel free to use the calculator on the home page. 

x-3(x+5)=-(3x+20)

$$\\-3(x+5)=-3x+-15=-3x-15\\\\
-(3x+20)=-1(3x+20)=-3x+-20=-3x-20\\\\
so\\
x-3(x+5)=-(3x+20)\\
x-3x-15=-3x-20\\
-2x-15=-3x-20$$

And you can take it from there.

Notice that if you multiply a bracket by a negative number, everything inside the bracket changes sign. 

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