{ 7,X,Y} i.p { 15,35,21} => 7*15= 35*x = 21*y
35x=21y=105
x= 105 \ 35=3
y= 105\ 21=5
X + Y = 3+5 = 8
Proprietate : Daca ( a,b) invers proportionale cu ( 2 ,3 ) , inseamna ca [tex] \frac{a}{ \frac{1}{2} } = \frac{b}{ \frac{1}{3} } \ \textless \ =\ \textgreater \ 2a=3b [/tex]
