i zi: x-1/4·x=x-x/4=(4x-x)/4=3x/4
II zi: 3x/4-1/4·3x/4=3x/4-3x/16=(12x-3x)/16=9x/16
9x/16=27
x=(27·16)/9
x=48 lei pretul initial
I zi a cheltuit :48/4=12 lei
a ramas cu 48-12=36 lei
II zi a cheltuit:36/4=9 lei
36-9=27 lei a ramas
in cele 2 zile a cheltuit 12+9=21 lei