prima zi = 15%
a doua zi = 15x3=45%
a treia zi = 80 lei
15%+45%+80=100
60%+80=100%
100%-60%=80 lei
40%=80 lei
40%.....................................80 lei
100%................................... x lei
x=100x80:40=8000:40=200 lei suma totala
200x15:100=3000:100=30 lei reprezinta 15%
R: Andrei a cheltuit in prima zi 30 lei