I'm not sure, but it's probably that Mary bakes faster than Sarah?
Explanation
We must the tangent line at x = 3 of the function:

The tangent line is given by:

Where:
• m is the slope of the tangent line of f(x) at x = h,
,
• k = f(h) is the value of the function at x = h.
In this case, we have h = 3.
1) First, we compute the derivative of f(x):

2) By evaluating the result of f'(x) at x = h = 3, we get:

3) The value of k is:

4) Replacing the values of m, h and k in the general equation of the tangent line, we get:

Plotting the function f(x) and the tangent line we verify that our result is correct:
Answer
The equation of the tangent line to f(x) and x = 3 is:
Answer: -9.1
Explanation
-3x +12.4=39.7
First minus 12.4 from both sides
-3x +12.4=39.7
-12.4 -12.4
-3x=27.3
Now devid both sides by -3
X= -9.1
There are 4 quarts in a gallon