The life span would be 24 months.
The formula for z-scores is:
Using the information we're given we have:
Multiply both sides by 8 to cancel it:
-3(8) = ((X-48)/8)*8
-24 = X-48
Add 48 to both sides:
-24+48 = X-48+48
24=X
If your asking for the total, 2 1/4 has to change so there’s common denominator, so 2 1/4 x 2 = 2 2/8. Then add 2 2/8 + 2 1/8= 4 3/8
9,504
31,396.86
8,487.42
7,854