Answer:
Step-by-step explanation:
Given that among 500 freshmen pursuing a business degree at a university, 315 are enrolled in an economics course, 213 are enrolled in a mathematics course, and 123 are enrolled in both an economics and a mathematics course.
From the above we find that
a) either economics of Math course is

Out of 500 students 405 have taken either Math or Economics
Hence
c) student who have taken neither = 
Exactly one course is either math or economics - both
= 
1 week is 7 days.
3 weeks = 21 days. Answer D. is correct.
A hour is 3600 seconds
24 hours ( a day ) is 86400 seconds
21 days is 1814400 seconds. * This is not an option *
Since 24 hours are in a day 24 hours x 21 days is 504 hours
Answer A. is correct
504 hours x 60 minutes per hour is 30240
Answer B. is correct. These are all the correct answers, A,B, and D.
Answer: she would catch up with Tom in 1 hour.
Step-by-step explanation:
Let t represent the time it will take for Mary to catch up with Tom.
Tom leaves his boat from a dock and travels at a rate of 25 miles per hour.
Distance = speed × time
Distance travelled by Tom in t hours is
25 × t = 25t
Ten minutes later, Mary leaves the same dock in her speedboat and heads after Tom. Converting 10 minutes to hours, it becomes 10/60 hour
Time spent by Mary is (t - 10/60) hours. If she travels at a rate of 30 miles per hour, it means that the distance that she would travel in
(t - 10/60) hours is
30(t - 10/60)
= 30t - 5
By the time she catches up with Tom, they would have covered the same distance. It means that
25t = 30t - 5
30t - 25t = 5
5t = 5
t = 5/5 = 1 hour
The value would be more than c
80+10x is the expression. To find the cost for 9 guests, simply plug in 9 for x. This becomes an equation reading 80+10(9)=170. The total cost for 9 guests is $170.00.