Se adopta notatia s, suma de bani totala.
Prima zi : s1 = 60% * s + 40
A doua zi: s2 = 30%* ( s - s1) + 48
A 3-a zi: s3 = s - s1 - s2 = 92
Inlocuim in ultima relatie
92 = s - ( 60% * s + 40) - ( 30% * (s - ( 60% * s + 40)) + 48)
92 = s - 60/100 *s - 40 - ( 30/100*(s-60/100*s-40)+48)
92 = s - 0.6*s - 40 - 0.3*s + 0.18*s + 12 - 48
92 + 40 - 12 + 48 = s*(1-0.6-0.3+0.18)
168 = s*0.28
s = 600 lei
