f=35% elevi
b=35%+420
35+35=70 100%-70%=30%
420=30%
30%.................420
100%.................x
a) x=420*100/30=42000/30=4200/3=1400
x=1400 elevi sunt in tabara
b) f=35%.........x
100%..............1400
x=35*1400/100=490 fete
b=35%+420=490+420=910 baieti
c) 420:2=210 ar trebui sa fie acel nr.
490+210=700 fete
910-210=700 baieti
nr fetelor = nr baietilor