Răspuns :
21,09=2109/100
57/100x=2109/100
x=2109/100x100/57
x=2109/57
x=37
57/100x=2109/100
x=2109/100x100/57
x=2109/57
x=37
[tex] \frac{57}{100} \times x = 21.09 \\ 57x = 21.09 \times 100 \\ x = \frac{2109}{57} \\ x = 37[/tex]