Two groups went hiking, leaving at the same time and arriving back at the same time. while one group moved away at the speed 6 mph and then moved back at the speed 4 mph, the other group moved all the way with the same speed. what was the speed of this second group, if both groups covered the same total distance, 24 miles?

This uses the formula d = r * t
First group

This group determines the time to be used by both groups.
t = d/r
t = 24 / 6
t = 4 hours hours going there.

t = 24 / 4
t = 6 hours 
Total time taken is 6 hours + 4 hours = 10 hours.

Group two

t = 10 hours.
d = 48 miles (remember, they have to come back).
r = 48 miles / 10 hours
r = 4.8 miles / hour
For humans, that actually is quite quick.

Can you provide the tape diagram?

First, think of what you know. you know that the number t the end of the equation will need to be subtracted because it is the money he lost from buying the lawn mower. and your first two weeks have negative profit, so that tells you that c and d are wrong. now you can plug any of the weeks into a and b to see which one works. i'll start with plugging week 1 into a.this isn't right because it says your answer for week one should be -90.so now we need to try the same thing with b.this one got you the right answer, (sometimes if you only check with one of the weeks multiple will work so you need to check with more of the weeks, but it worked out fine here)this means that b is the correct answer.let me know if you need more clarification. i hope this : )