Question

The weight of an object on a particular scale is 175.2 lbs. The measured weight may vary from the actual weight by at most 0.1 lbs. What is the range of actual weights of the object

Answer 1

"The measured weight may vary from the actual weight by at most 0.1 lbs"

so it can be, at most, 0.1 pounds higher than 175.2
and, at least, 0.1 pounds lower than 175.2

so adding 175.2 + 0.1 will give you the upper bound and subtracting 175.2-0.1 will give you the lower bound