7*X(number of students)=y(total cost)
The independent variable is the number of students and the dependent variable is the cost in dollars. I hope I helped!
Three hundred and twenty seven point seven nine

Step-by-step explanation:
We start by applying the Pythagorean theorem to the ladder, with its length L as the hypotenuse:

where x is the vertical distance from the top of the ladder to the ground and y is the horizontal distance from the bottom of the ladder to the wall. Taking the derivative of the above expression with respect to time, we get

Solving for dx/dt, we get

We know that

when x = 6 ft. So the rate at which the top of the ladder is going down is


The negative sign means that the distance x is decreasing as y is increasing.
Answer:
x=70 y=110 z=30 is all of the variables