1.
25/a=b/0.3 ⇔ a*b=1.25*0.3 ⇔ a*b= 0.375
100.a*b=?
100*0.375= 37.5
2.
450 lei................100%
x lei....................100+15=115%
x= 450*115:100= 517.5 lei
3.
a+b+c=122
a=75/100*b deci a= 3/4b= 3/4*30/100 c= 3/4*3/10c=9/40 c
b=30/100c
9/40c+3/10c+c=122
(9c+12c+40c)=122*40
61c=122*40
c=2*40 a=9/40*80 b=3/10*80
c=80 a= 18 b=24
verific: 80+24+18=122