Answer:
The value of x component changes at a rate of
units per second
Step-by-step explanation:
We are given that 
Differentiating on both sides with respect to time we get

It is given that
Solving for
we get

Answer:
$84 per person because if multiply 84 by 4 its 168
The answer is B. That is not a valid way to sample as it is not randomly selected.
You can see if the other angles add up to 180 or 360 degrees (depending on shape) then add them to make it the number, for example, if a triangle has a right angle, then the other 2 angles are 45 degrees, knowing that EVERY triangle's angles add up to 180 degrees.