6) a/18=b/25 => a/b=18/25 =18*4/25*4=72% ;
5) x/y=1,(3) =...= (13-1)/9=12/9=4/3
=> x=4k si y=3k inlocuim ...
(2*4k - 3k)/(3*4k+3k)=5k/15k=1/3 .
4) x;2;6;9 formeaza o proportie astfel ca x ∈N !
(1)... 6/2 = x/9 => x = 6*9 / 2 = 27∈ N ;
(2)... 9/6 = x/2 => x = 9*2 / 6 = 3 ∈ N ;
A = {3 ; 27}
3) 12% ...... 9 t
100% ... x
------------------- marimile sunt direct proportionale !
x = 9*100 : 12 = 75 t .
