Are you looking for slope?
if u r the slope is -6/3
y = 12x + 10
Assuming that your question is multiple choice, the variables might be different.
The reason that it's represented as 12x + 10 is because there is a flat fee of $10 when you sign up. From then on afterward, every month you pay $12.
In this equation, the variable 'y' represents the total cost, while 'x' represents the number of months this service was in use.
Answer: dydx=2sec2(x)tan(x)
Step-by-step explanation:

Above, I changed the fraction form of x and y into exponential form so it is easier to see the differentiation. Now, we can differentiate:

Now that we have dy/dx, we can plug in the x, which is 4, and the y, which is 4/19. We know these values of x and y because your question stated y(4) = 4/19.