a+b+c=95
a/5=(b+2)/12=(c+3)/18
a/5=(b+2)/12
12a=5(b+2)
12a=5b+10
a=(5b+10)/12
(b+2)/12=(c+3)/18
18 (b+2)=12 (c+3)
18b+36=12c+36
18b=12c
c=18b/12
=>
(5b+10)/12+b+18b/12=95
23b+10+12b=1140
35b=1130
b=1130/35
b=226/7
a=(5*226/7+10)/12
a=[(1130+70)/7]/12
a=1200/7*1/12
a=100/7
c=(18*226/7)/12
c=4068/7*1/12
c=339/7
verificare :
100/7+226/7+339/7=665/7=95