suma initiala= n
in prima zi: cheltuieste n/4 => ramane cu 3n/4 lei
a doua zi: cheltuieste (3n/4)/4=3n/16 => ramane cu 9n/16 lei
a treia zi: cheltuieste 6/10 x 9n/16 = 54n/160
ramane cu 9n/16 - 54n/160= (90n-54n)/ 160 (am adus la acelasi numitor)
(90n-54n)/160= 36n/160
acest 36n/160= 270=> n= 160x270/36 => n=1200 lei (suma initiala)
