Answer: [tex]12.39\ kg[/tex]
Step-by-step explanation:
Given
Luis used 590 gm of flour each day
If he continues to use it for 3 weeks
A week has 7 days; so 3 weeks have 21 days
The flour used in 21 days
[tex]\Rightarrow 21\times 590\\\Rightarrow 12,390\ g\ \text{or}\ 12.39\ kg[/tex]
Thus, [tex]12.39\ kg[/tex] of flour is used in 3 weeks