Răspuns:
Explicație pas cu pas:
S = suma
Prima cheltuiala 3S/7
rest S - 3S/7 = 7S/7 - 3S/7 = 4S/7
A doua cheltuiala 3/5*4S/7 = 12S/35
3S/7 + 12S/35 + 16 + 24 = S
15S/35 + 12S/35 + 40 = S
27S/35 + 40 = S
S - 27S/35 = 40
35S/35 - 27S/35 = 40
8S/35 = 40
S = 35*40/8 = 35*5 = 175 lei