Given a mean of 5 and a standard deviation of 2, compute
the -3, -2, -1, (mean), +1, +2, and +3 points along the baseline of the
curve (you can assume the curve is normal).  

Do the same when the mean is 50 pounds and the standard deviation is 4.5 pounds.  

Do the same when the mean is 8 seconds and the standard deviation is  2 seconds.  

Now take one of the distributions above and show how many cases fell
in each standard deviation divisions given the original distribution
contained 1,000 cases.

These three questions are exactly the same.  I'll take the pounds one.

I'm assuming when they say "-3" they're talking about -3 standard deviations

   -3   is 50 - (3 * 4.5)= 36.5
   -2   is 50 - (2 * 4.5)= 41.0
   -1   is 50 - (1 * 4.5)= 45.5
  mean  is 50
   +1   is 50 + (1 * 4.5)= 54.5
   +2   is 50 + (2 * 4.5)= 59.0
   +3   is 50 + (3 * 4.5)= 63.5

From a standard normal distribution table:
1.0 standard deviations .3413
2.0 standard deviations .4772
3.0 standard deviations .4987

from    to
-3      -2 :   1000 * (.4987-.4772) =  21.5 cases
-2      -1 :   1000 * (.4772-.3413) = 135.9 cases
-1       0 :   1000 * (.3413-0) = 341.3 cases

As you get closer to the mean, the number of cases increases.

If you add these three numbers up you get 498.7, which is almost half
of the 1000. The remaining 1.3 cases lie to the left of -3 standard
deviations.

For the plus side of the distribution, same thing in reverse:

from    to
0       +1 :   1000 * (.3413-0) = 341.3 cases
+1      +2  :   1000 * (.4772-.3413) = 135.9 cases
+2      +3 :   1000 * (.4987-.4772) =  21.5 cases

hope this helps