Question 682162
This question is related to simultaneous linear equations in two variables.

Solution:
Let x be the number of working days 
and y be the number of absent days.

since total number of days are 20 , 
hence we get: x + y = 20 

now second condition says 
cost for working days is $80 , hence total cost is 80x 

cost reduced for absent days is $ 6 , 
hence total cost reduced is 6y 

now total amount obtained is $ 826 
therefore the equation is: 80x - 6y = 826 

now we can solve by elimination method:
 x + y = 20   multiply by 6 
we get 6x + 6y = 120 
and    80x -6y = 826 
now add both the equation we get :

86x = 946 

x = 946/86
x = 11

plug x = 11 in first equation and get y?
x + y = 20 
11 + y = 20 
y = 9 

hence 11 are working days 
and so he remain absent for 9 days.