Answer: 125lb < M < 155 lb
Explanation:
The mean mass is 140 lb, and the deviation must be less than 15 pounds (exactly 15 is not accepted).
Then (140lb + 15lb) is not alowed, and (140lb - 15lb) is not alowed.
Then we can define M = mass.
We have the two equations:
M < 140lb + 15lb
M < 155lb
And
M > (140lb - 15lb)
M > 125lb
If we write these two relations togheter, we get:
125lb < M < 155 lb