Answer:
(a)Therefore the value of x=
(b) Therefore the value of x 
Step-by-step explanation:
Horizontal tangent line: The first order derivative of a function gives the slope of the tangent of the function. The slope of horizontal line is zero.If the slope of tangent line is zero then the tangent line is called horizontal tangent line.
(a)
Given function is,

Differential with respect to x

For horizontal tangent line, f'(x)=0
3+ 3 cos x= 0
⇒3 cos x=-3
⇒cos x=-1
⇒x = 180° 
Therefore the value of x=
(b)
Given that, the slope is 3.
Then,f'(x)=3
3+ 3 cos x= 3
⇒3 cos x= 3-3
⇒cos x=0
⇒x = 90° 
Therefore the value of x 
D. 35 is the answer. Since we know that 14=2k based on the knowledge given in the first part of the equation, we can solve for K. We learn that K=7. Then, we can substitute K into the second equation: y=(7)(5) which is 35.
It is 57/8 ! You should use this math calculater! it's called calculater soup!
The answer would be 3 because both y points are equal so you look at the difference between the x points. The difference of 4 and 7 is 3. If this is right could I possibly have brainliest? Hope this helped!! :)