Answer:
110 [%].
Step-by-step explanation:
if the initial area is 24 m² and final area 50.4 m², then the required percentage can be calculated as:
[tex]\frac{50.4}{24}*100-100=110[/tex] ,
where 50.4/24*100 - the final percentage.
P.S. It means, the final value of the paint is 3*2.1=6.3 [liters].