Answer:
a. 125 – 7d
Step-by-step explanation:
Let d be the number of days.
<u>Given the following data;</u>
Total distance (month) = 125 miles
Distance covered per day = 7 miles
To determine how many miles he has left to run after running for "d" days, this mathematical expression can be used;
Total distance - distance covered per day = number of miles remaining

THIS IS THE COMPLETE QUESTION BELOW
The demand equation for a product is p=90000/400+3x where p is the price (in dollars) and x is the number of units (in thousands). Find the average price p on the interval 40 ≤ x ≤ 50.
Answer
$168.27
Step by step Explanation
Given p=90000/400+3x
With the limits of 40 to 50
Then we need the integral in the form below to find the average price
1/(g-d)∫ⁿₐf(x)dx
Where n= 40 and a= 50, then if we substitute p and the limits then we integrate
1/(50-40)∫⁵⁰₄₀(90000/400+3x)
1/10∫⁵⁰₄₀(90000/400+3x)
If we perform some factorization we have
90000/(10)(3)∫3dx/(400+3x)
3000[ln400+3x]₄₀⁵⁰
Then let substitute the upper and lower limits we have
3000[ln400+3(50)]-ln[400+3(40]
30000[ln550-ln520]
3000[6.3099×6.254]
3000[0.056]
=168.27
the average price p on the interval 40 ≤ x ≤ 50 is
=$168.27
Percent decrease=decrease/original times 100
decreas=860-790=70
original=860
percent decrease=70/860 times 100
percent decrease=0.0813953 times 100
percent decrease=8.13953
about 8%