[tex] \left \{ {{f= \frac{3}{4}b } \atop {f+4=b}} \right. [/tex]
[tex] \frac{3}{4}b+4=b [/tex]
[tex] \frac{3}{4}b+ \frac{16}{4}= \frac{4}{4}b [/tex]
[tex]3b+16=4b[/tex]
[tex]16=4b-3b[/tex]
[tex]16=b[/tex]
[tex]f= \frac{3}{4}*16 [/tex]
[tex]f=12[/tex]
In clasa erau initial 16 baieti si 12 fete