We are given

where
y is the cost in dollars
x is distance in dollars
now, we can find derivative



so,

So,
the rate of change of the cost in dollars with respect to the number of miles is 1.5.........Answer
The LCM is the lowest number that is a multiple of all three numbers.
First, list the multiples of each number
8: 8, 16, 24, 32,40 48, 56, 64, 72, 80, 88, 96, 104, 112, 120
10: 10, 20, 30 40, 50, 60, 70, 80, 90, 100, 110, 120
12: 12, 24, 36, 48, 60, 72, 84, 96, 108, 120
The LCM is 120 because there is no lower number that is a multiple of all three numbers.
Hope this helped!
Answer:
Her usual rate is 0.8333 miles per hour.
Step-by-step explanation:
The velocity formula is given by:

In which d is the distance and t is the time.
She completed the first half of the walk 1 mi/h faster than usual
Her usual rate is v. 1mph faster is v + 1.
The second half of the walk 2 mi/h slower than the first half.
The first half is v + 1.
2mph slower is v + 1 - 2 = v - 1. Then
Total rate:
7.2 hours, and 6 miles. So
One half is v+1 and the other is v - 1. This is why each is multiplied by 0.5.



Her usual rate is 0.8333 miles per hour.