Odpowiedź :
1.
100% - x
80% - 320
80%*x = 100% * 320
x= (100% * 320) / 80%
x= 400
2.
100% - x
7% - 28
x= ( 100% * 28 ) / 7%
x= 2000
100% - x
80% - 320
80%*x = 100% * 320
x= (100% * 320) / 80%
x= 400
2.
100% - x
7% - 28
x= ( 100% * 28 ) / 7%
x= 2000