I zi : 30/100 • s (simplifici) -> 3s/10
II zi : 40/100 • s ( simplifici) -> 2s/5
III zi : 1/4 • s -> s/4
b) 3s/10 + 2s/5 + s/4 + 100 = s (aduci la acelasi numitor comun - 20)
6s + 8s + 5s +2000 = 20 s
19s + 2000 = 20s
s = 2000 lei
a) in ziua III cheltuie cel mai putin, 25/100