Since the bolts need to be within 0.2 mm of 12 mm, that means that the length of the bolts are anywhere between 12 mm + 0.2 mm and 12 mm - 0.2 mm.
1. Since they are within 0.2 mm, and since it doesn't specify if they are plus or minus, the bolts can be at lengths anywhere from 12.2 mm to 11.8 mm.
a) Since the bolts are within 0.2 mm of 12 mm, that means that the longest would be 12 mm + 0.2 mm which is equal to 12.2 mm.
b) Since the bolts are within 0.2 mm of 12 mm, the shortest bolt possible would be 0.2 mm smaller than 12 mm, which is equal to 12 mm - 0.2 mm which is 11.8 mm.
