a+b+c= 21
20% din a= 20/100 * a= 1/5 * a = a/5
25% din b= 25/100 * b= 1/4 * b= b/4
30% din c= 30/100 * c= 3/10 * c= 3c/10
a/5 ; b/4 ; 3c/10 dp cu 1/2 ; 35/48; 1
a/5/1/2 = b/4/35/48= 3c/10/1 =k
a/5 * 2/1 = b/4 * 48/35 = 3c/10 * 1= k
2a/5 = 12b/35 = 3c/10 =k
a=5k/2
b=35k/12
c=10k/3
5k/2 + 35k/12 + 10k/3 = 21 aducem la acelasi numitor
30k + 35k + 40k = 252
105k=252
k= 252/105
a= (5 * 252/105)/2= 252/21/2= 252/21 * 1/2= 126/21 =6
b= (35 *252/105)/12= 252/3/12= 252/3 * 1/12= 21/3=7
c= (10*252/105) /3= (2*252)/21/3= 2*252/21 * 1/3= 2*84/21 = 2*4 =8
