Răspuns :
3. 7/a = b/8 ; ab = 56 ; 42/ab = 42/56 = 21/28 ;
5. regula de trei simpla
35%........21 caiete
100%........n caiete ; n = 21x100/35 = 2100/35 = 60 caiete ;
[tex]3)\frac{7}{a} =\frac{b}{8} =>ab=7*8=>ab=56\\ \\ \frac{42}{ab} =\frac{42}{56} =\frac{3}{4} =0,75\\ \\ 5) \frac{35}{100} x=21=>35x=21*100=>x=2100:35=>x=60 c aiete.vandute[/tex]