notam cu x suma initiala
prima zi = x/2 + 1000
rest dupa prima zi = x/2 - 1000
a doua zi = (x/2 - 1000)× 1/4 + 1000
suma ramasa = 2000
x = x/2 + 1000 + (x/2 - 1000)× 1/4 + 1000 + 2000
x = x/2 + 1000 + x/8 - 1000/4 + 1000 + 2000
x - x/2 - x/8 = 4000 - 250
(8x - 4x - x)/8 =3750
3x/8 = 3750
x = 3750×8/3
x = 10000 lei