The answer is B:40 hours. You take 200 divided by 20 to get 10 (the amount of 20 page sections he needs to read) and then multiply 10 by 4 (the speed he reads).
Its a. An enlargment on a scale of 3/1.
X= -10
You may review the image Ive attached to see how I got this answer.
Step-by-step explanation:

We start with Left hand side
We know that csc(x) = 1/ sin(x)
So csc(2x) is replaced by 1/sin(2x)

Also we use identity
sin(2x) = 2 sin(x) cos(x)

4 divide by 2 is 2
Now we multiply top and bottom by sin(x) because we need tan(x) in our answer



We know that sinx/ cosx = tan(x)
Also 1/ sin(x)= csc(x)
so it becomes 2csc^2(x) tan(x) , Right hand side
Hence verified