Răspuns :
35.........................................................
x:21=y si rest 14
x=21y+14
x=7(3y+2) deci divizibil cu 7
30<x<50
30<21y+14<50
y>(30-14)/21
y>16/21
y<(50-14)/21=36/21
alegem y=1
x=21*1+14=35
x=21y+14
x=7(3y+2) deci divizibil cu 7
30<x<50
30<21y+14<50
y>(30-14)/21
y>16/21
y<(50-14)/21=36/21
alegem y=1
x=21*1+14=35