Question 437074
The standard distance formula is:  d=rt, where d=distance, r=rate, and t=time.
.
We're told:
3/8 mi = 15/2 min * r miles/min
.
Note that 7 and 1/2 minutes = 15/2 minutes
.
3/8 = 15/2 * r
Multiply both sides by 8
3 = 8*(15/2) * r
3 = 4*15*r
3 = 60r
Divide both sides by 60
3/60 = r
so
r = 3/60
r = 1/20
That means the person is walking at 1/20 of a mile per minute.
"Per minute" is very important because it would be easy to forget and think in "miles per hour."
.
Now that we have r, we can plug it into the next distance equation to determine "how long" it will take to walk 2 miles.
2 = 1/20*t
.
Multiply both sides by 20 to remove the denominator.
.
40 = t
t = 40
.
This suggests it will take 40 minutes to walk 2 miles.
.
Always check your answer!
In this case we can use proportions.
Is the proportion:  3/8 : 15/2
the same value as:  2 : 40?
Simplifying, 2 : 40 is the same as 1 : 20, which equals 0.05.
So, let's check (3/8)/(15/2).
Using a calculator we find that (3/8)/(15/2) = 0.05.  
The proportions are equal, so we know the answer is correct.
.
Review the question to make sure you give a clear answer.
.
Answer:  It will take 40 minutes to walk 2 miles.
.
Done.