You have the following function:

Derivate implictly the previous expression, as follow:

Where you have used that:

Then, the implicit derivative of the given expression is:

Next, solve for y' as follow:

Work shown above! Box a is 240 lbs Box b is 120 and Box c is 150 lbs hope this helps c:
Answer:
41
Step-by-step explanation:
Step 1:
12x - 7 Equation
Step 2:
12 ( 4 ) - 7 Input x value
Step 3:
48 - 7 Multiply
Answer:
41 Subtract
Hope This Helps :)