Answer :
If f = price of filing cabinet and c = price of cupboard we can make up the equation
2f + 4c =800
we also know that f = 3c, so can substitute that into equation
2(3c) +4c = 800
6c + 4c = 800
10c = 800
c = 80
f = 240
2f + 4c =800
we also know that f = 3c, so can substitute that into equation
2(3c) +4c = 800
6c + 4c = 800
10c = 800
c = 80
f = 240