John takes 15 minutes to get to school. The bell rings at 9:00a.m. John wants to get there 5 minutes before the-bell. At what time should John leave home?

8:40 a.m.

Step-by-step explanation:

Let's start by finding the time John should arrive at school.

9:00 a.m. - 5 minutes = 8:60 a.m. - 5 minutes = 8:55 a.m.

Note that there are 60 minutes in an hour

Now, we find the time he should leave home...

8:55 a.m. - 15 min = 8:40 a.m.

Therefore John should leave at 8:40 a.m.

Another way to solve this problem:

John needs to leave home in "x" minutes before 9:00 a.m. to arrive when the bell rings (9:00 a.m.). To find "x", we need to add 15 and 5 to get:

15 min + 5 min = 20 min.

Therefore he must arrive 20 minutes before 9:00 a.m.

9:00 a.m. - 20 min = 8:40 a.m.

Therefore John should leave at 8:40 a.m.

Brielle will run the marathon faster.

Brielle = 104.8 minutes  

Joshua = 157.2 minutes

Step-by-step explanation:

Speed rate = distance /time

Brielle = 1.25 /10 = 0.125 miles per minute

Joshua = 1.5/18 = 0.083333 =1/12 miles per minute

Since 0.125 (Brielle) > 1/12 (Joshua)

Brielle will run the marathon faster.

To calculate the time that takes each one to run the entire race (13.1 miles)

Time= distance / speed

Feel free to ask for more if needed or if you did not understand something.