The correct answer is A.
You have direct variation if x and y are modeled by the equation

In this case, m is the constant of proportionality. So, if the constant has to be 2, the equation becomes

A side note: Actually, option C has a constant of proportionality of two as well, except the roles of x and y are interchanged. I chose option A because usually you want the y = mx form, but the names of the variables are obviously meaningless.
Answer:
Looks like all of your questions have been answered.
71/3=23.6
36/7=5.14
23.6-5.14=18.46
So, the correct answer is 18.46
Answer:
Simplifying
4cos(10x) + 2 = 2
Remove parenthesis around (10x)
4cos * 10x + 2 = 2
Reorder the terms for easier multiplication:
4 * 10cos * x + 2 = 2
Multiply 4 * 10
40cos * x + 2 = 2
Multiply cos * x
40cosx + 2 = 2
Reorder the terms:
2 + 40cosx = 2
Add '-2' to each side of the equation.
2 + -2 + 40cosx = 2 + -2
Combine like terms: 2 + -2 = 0
0 + 40cosx = 2 + -2
40cosx = 2 + -2
Combine like terms: 2 + -2 = 0
40cosx = 0
Solving
40cosx = 0
Solving for variable 'c'.
Move all terms containing c to the left, all other terms to the right.
Divide each side by '40'.
cosx = 0.0
Simplifying
cosx = 0.0
The solution to this equation could not be determined.
Step-by-step explanation: