Answer:
The letter "b" indicates it is effective against flammable liquid fires.
Step-by-step explanation:
The letters on fire extinguishers represents the class of fire for which they can be used.
The letter "b" here indicate the b-1 extinguisher is effective against flammable liquid fires. These can be fires where cooking liquid , oil , gasoline , kerosene or paint.
B...
|-24+6|=18
Same for the other one.
Shade 3 boxes vertically and 5 boxes horizontally and then you have to use that to just solve the problem because the boxes represent the fractions