The capacity of the jug is 3.5 litres, correct to the nearest 0.1 litre. The capacity of a glass is 0.25 litres correct to the nearest 0.01...

The capacity of a jug is 3.5 l correct to the nearest 0.1
l. This places the volume of the jug between 3.50 l and 3.59
l

The capacity of a glass is 0.25 l correct to the nearest
0.01 l. This places the volume of a glass between 0.259 and 0.250
l

The maximum number of glasses that can surely be filled
is equal to the whole number that lies just below
3.50/0.259.

3.50/0.259 =
13.51

The required value of the greatest
number of glasses that can be surely filled is
13.