Question

dos quintos de x = 20

Answer 1

2x/5 = 20
2x= (20)×5
2x= 100
x= 50

Answer 2

2/5 de x = 20

x * 2/5 = 20

2x/5 = 20

2x = 20 * 5

2x = 100

x = 100/2

x = 50

Solución : 

50

COMPROBAMOS : 

2/5 de 50 : 

(2 * 50)/5

100/5

20

Es correcto.